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Kim, Kim, Lee, Yoon, Park, Lim, Yu, and Kim: Partial mesorectal excision can be a primary option for middle rectal cancer: a propensity score–matched retrospective analysis

Original Article

Published online: March 31, 2023

DOI: https://doi.org/10.3393/ac.2022.00689.0098

Partial mesorectal excision can be a primary option for middle rectal cancer: a propensity score–matched retrospective analysis

Ee Jin Kim, Chan Wook Kim, Jong Lyul Lee, Yong Sik Yoon, In Ja Park, Seok-Byung Lim, Chang Sik Yu, Jin Cheon Kim

Division of Colorectal Surgery, Department of Surgery, Asan Medical Center, University of Ulsan College of Medicine, Seoul, Korea

Correspondence to: Jin Cheon Kim, MD Division of Colorectal Surgery, Department of Surgery, Asan Medical Center, University of Ulsan College of Medicine, 88 Olympic-ro-43-gil, Songpa-gu, Seoul 05505, Korea Email: jckim@amc.seoul.kr
Received September 22, 2022       Revised November 15, 2022       Accepted November 23, 2022

© 2024 The Korean Society of Coloproctology

This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (https://creativecommons.org/licenses/by-nc/4.0/) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.
Abstract
Purpose
Purpose
Although partial mesorectal excision (PME) and total mesorectal excision (TME) is primarily indicated for the upper and lower rectal cancer, respectively, few studies have evaluated whether PME or TME is more optimal for middle rectal cancer.
Methods
Methods
This study included 671 patients with middle and upper rectal cancer who underwent robot-assisted PME or TME. The 2 groups were optimized by propensity score matching of sex, age, clinical stage, tumor location, and neoadjuvant treatment.
Results
Results
Complete mesorectal excision was achieved in 617 of 671 patients (92.0%), without showing a difference between the PME and TME groups. Local recurrence rate (5.3% vs. 4.3%, P>0.999) and systemic recurrence rate (8.5% vs. 16.0%, P=0.181) also did not differ between the 2 groups, in patients with middle and upper rectal cancer. The 5-year disease-free survival (81.4% vs. 74.0%, P=0.537) and overall survival (88.0% vs. 81.1%, P=0.847) also did not differ between the PME and TME groups, confined to middle rectal cancer. Moreover, 5-year recurrence and survival rates were not affected by distal resection margins of 2 cm (P=0.112) to 4 cm (P>0.999), regardless of pathological stages. Postoperative complication rate was higher in the TME than in the PME group (21.4% vs. 14.5%, P=0.027). Incontinence was independently associated with TME (odds ratio [OR], 2.009; 95% confidence interval, 1.015–3.975; P=0.045), along with older age (OR, 4.366, P<0.001) and prolonged operation time (OR, 2.196; P=0.500).
Conclusion
Conclusion
PME can be primarily recommended for patients with middle rectal cancer with lower margin of >5 cm from the anal verge.

Key words: Rectal neoplasms, Robot-assisted surgery, Proctectomy, Survival, Recurrence

INTRODUCTION
INTRODUCTION
Miles’ groundbreaking approach to abdominoperineal resection enlightened the first concept of mesorectal excision in 1908 [1]. The mesorectum was described as a clue to pelvic recurrence of rectal cancer, defining the principle of total mesorectal excision (TME) by Heald et al. [2]. Complete removal of the mesorectal fascia, the sites of potential tumor spread, in 50 patients with Dukes B/C rectal cancer who underwent TME resulted in a 2-year local recurrence rate of 0%. A local recurrence rate of ≤10% is generally expected if proper TME techniques are employed [3].
The completeness of mesorectal excision (complete mesorectal excision) is of prime importance, as resection at the muscularis propria plane results in ≥2-fold higher risks of both local and systemic recurrences than resection at the (intra)mesorectal plane [4]. However, routine TME along all levels of rectal cancer may be suboptimal, due to increased risks of morbidity, including ≥10% higher rates of anastomotic leakage and lower anterior resection syndrome than partial mesorectal excision (PME) [5–7]. Few studies have compared outcomes of PME and TME as a function of tumor location, other than narrative reviews suggesting that PME is optimal for upper rectal and rectosigmoid cancers, whereas TME is optimal for middle and lower rectal cancers [3, 5]. TME, however, may be confused with PME when dissection is performed down to the mesorectal end without complete excision of the mesorectum [8].
Furthermore, as TME included complete excision of mesorectal fascia, regardless of extent, TME indispensably excised adjacent tissues via en bloc excision including aggressive tumor deposits (ATDs) or suspicious invasion. Therefore, TME-associated histopathological changes correlate with R0 resection and consequent anorectal dysfunction needs to be reconsidered. Otherwise, incomplete lateral pelvic mesorectal excision was associated with increased local recurrence, indicating that complete lateral pelvic mesorectal excision is an indispensable component of quality TME in a previous study [9].
The current study was designed to compare prognostic and functional outcomes in propensity score–matched patients with middle and upper rectal cancer who underwent PME and TME. These findings further suggest the mandatory extent of mesorectal excision for middle rectal cancer.
METHODS
METHODS
Ethics statement
Ethics statement
This study was approved by the Institutional Review Board of Asan Medical Center (no. 2022-0683). All patients provided voluntary written informed consent for publication of the research details and clinical images. The study protocol conformed to the Declaration of Helsinki.
Patients and study design
Patients and study design
The medical records of the 1,402 consecutive patients who underwent robot-assisted curative-intent lower anterior resection (LAR) from 2010 to 2021 at Asan Medical Center (Seoul, Korea) were reviewed. Of these patients, 671 (47.9%) underwent LAR for middle and upper rectal cancers, with 437 undergoing PME and 234 undergoing TME. Patients were subsequently subjected to 1:1 propensity score matching by sex, age, clinical stage, tumor location, and neoadjuvant treatment (Table 1). Tumor location was divided into lower (≤5 cm from the anal verge), middle (>5–10 cm), and upper (>10–15 cm) rectum [10]. The primary endpoint was mesorectal quality in the PME and TME groups. Secondary endpoints were anorectal function 12 to 24 months after surgery, and 5-year cumulative recurrence rate, disease-free survival (DFS), and overall survival (OS) in patients aged ≤80 years with clinical stage ≤III disease, according to the American Joint Committee on Cancer (AJCC) Staging Manual (8th ed; https://www.cancer.org/). A detailed study scheme, with inclusion and exclusion criteria, is illustrated in Fig. 1.
Operation and adjuvant treatment
Operation and adjuvant treatment
Neoadjuvant treatment was recommended for patients with clinical stage III or T4 middle rectal cancer, with most of the tumor located below the peritoneal reflection. In contrast, upfront surgery was also considered for patients with cT3a/bN1–2, classified as low to intermediate risk based on the European Society for Medical Oncology (ESMO) guidelines [10, 11]. Final treatment modality was determined after informed discussions between patients and surgeons, with recommendations by the multidisciplinary team. Neoadjuvant therapy and postoperative chemoradiotherapy for middle rectal cancer, consisting of long-course radiotherapy with boost chemotherapy, were as described [11]. Patients with pathologic AJCC stage (pStage) ≥III or high-risk stage II cancer [10] were administered adjuvant chemotherapy, consisting primarily of 5-fluorouracil/leucovorin or capecitabine, but sometimes oxaliplatin (Table 1).
Operative procedure and quality assessment
Operative procedure and quality assessment
TME extent was determined according to tumor location and distal resection margin (DRM). Briefly, the inferior mesenteric artery was ligated and excised immediately after left colic artery bifurcation (low ligation), followed by downward dissection, alternating between the right and left sides in a spiral manner. Particular attention was needed for mesorectal excision posterior to Denonvilliers fascia, and laterally at the fusion of the proper rectal fascia and prehypogastric fascia wrapping the inferior hypogastric nerves, preserving the pelvic autonomic nerves (Fig. 2). TME was completed at the end of the mesorectal fascia just above the anorectal canal. By contrast, PME consisted of mesorectal excision transverse to the rectum depending on the DRM, which was conventionally defined as 2 to 4 cm for middle and upper rectal cancers [12]. Completeness of mesorectal excision was assessed by examining mesorectal quality, including bulk, defects, coning, and circumferential resection margin (CRM) [4]. We conveniently designated near-complete and incomplete TME as “inappropriate” mesorectal excision in contrast with complete mesorectal excision, as previously described [11]. Additional excision was considered for tumors with high-risk mesorectal fascia, consisting primarily of threatened mesorectal fascia (c/pT4) and suspicious invasion of the adjacent viscera. Concurrent diversional ileostomy was installed depending on the surgeon’s discretion, particularly in patients who have undergone preoperative chemoradiotherapy and a complicated procedure. All operations were performed by a senior colorectal surgeon sufficiently experienced with robot approaches. The entire procedure, with particular attention to TME extent and quality, was reexamined through video records and gross photographs.
Postoperative evaluations
Postoperative evaluations
All patients were followed up periodically every 3 to 6 months for the first 5 postoperative years, and every 2 years thereafter. The severity of surgical complications was evaluated using the Clavien-Dindo classification (https://drcesarramirez.com/). Anorectal function was analyzed in patients aged ≤65 years by measuring Fecal Incontinence Score according to Wexner method (https://www.mdcalc.com/) and by high-resolution anorectal manometry (complete performance rate, 93.7%). Incontinence and manometric parameters, including mean resting pressure (MRP), maximal squeezing pressure (MSP), urge to defecate volume (UDV), and maximal tolerance volume (MTV), were examined preoperatively, and 6 to 12 and 12 to 24 months after primary and restorative surgery, respectively. Recurrence or survival >5 years after surgery and 2-year functional outcomes were assessed in propensity score–matched groups (Table 2). Median follow-up period was 57 months (interquartile range [IQR], 27–82 months).
Statistical analysis
Statistical analysis
To reduce potential bias caused by confounding, the 2 groups were subjected to 1:1 propensity score matching using the nearest-neighbor method (Table 2). Clinicopathological and operative features were compared using 2-tailed Fisher exact test, and continuous variables were compared using paired Student t-test. Potential associations between operation-associated and prognostic outcomes were reanalyzed by binomial logistic regression. OS and DFS were analyzed using the Kaplan-Meier method and compared by the log-rank test, and significant variables were validated using a Cox proportional-hazards regression model. All statistical analyses were performed using IBM SPSS ver. 21 (IBM Corp), with P<0.05 defined as statistically significant. All results were calculated for the propensity score–matched groups, unless otherwise specified.
RESULTS
RESULTS
Overall clinicopathological features in all patients undergoing PME or TME
Overall clinicopathological features in all patients undergoing PME or TME
Clinicopathological and operative findings were compared in the PME and TME groups (Table 1), and several differences of all patients were detailed. Complete mesorectal excision was achieved in 617 of the 671 patients (92.0%), with no difference between the PME and TME groups. Comparisons of pinned and formalin-fixed samples from the PME and TME groups showed no significant differences in DRM length (36 mm vs. 34 mm, P=0.189), proximal resection margin (83 mm vs. 88 mm, P=0.070), and total lymph node harvest (21 vs. 20, P=0.377). Low ligation was performed mostly to excise the inferior mesenteric artery (94.9%) in both groups. Additional excision of adjacent viscera was required to achieve R0 resection in 41 patients, with no difference between the groups. Partial excision of Denonvilliers and parietal pelvic fascia, en bloc with the rectum and mesorectum, was most frequent (65.9%). Postoperative complication rate was somewhat higher in the TME than in the PME group (21.4% vs. 14.5%, P=0.027), but did not differ by severity grade. Anastomotic leakage did not differ in the PME and TME groups, whereas stricture rate tended to be higher in the TME group (0.5% vs. 2.1%, P=0.054). No patient in either group died ≤1 month after surgery. Several parameters that differed in the PME and TME groups were no longer different after propensity score matching, except for DRM length (P=0.001), the transient diversion rate (P=0.001), and hospitalization (P=0.007) remained greater in the TME group. Fewer than 1/3 of propensity score–matched patients received either neoadjuvant treatment or postoperative chemoradiotherapy, with no difference between the 2 groups. Of the 316 patients with middle rectal cancer, 137 (43.4%) underwent PME and 179 (56.6%) underwent TME. The mean length of the anorectal canal in 200 consecutive patients was found to be 3.2 cm (range, 2–5 cm), with no difference between male and female patients.
Cumulative recurrences in the propensity score–matched PME and TME groups
Cumulative recurrences in the propensity score–matched PME and TME groups
In the total propensity score–matched cohort, the 5-year cumulative local and systemic recurrence rates were 4.8% and 12.2%, respectively. Comparative recurrences in propensity score–matched patients are shown in Table 3. Local recurrence rate (P>0.999) and systemic recurrence rate (P=0.181) in patients with middle/upper rectal cancer did not differ between the PME and TME groups. Although local recurrence rate (5.1% vs. 8.9%, P=0.534) in patients with middle rectal cancer did not differ in the PME and TME groups, systemic recurrence rate (7.6% vs. 22.8%, P=0.013) differed significantly in these groups. The rate of systemic recurrence was about 5-fold higher in patients with local recurrence than those without it (55.6% vs. 10.1%, P=0.002). Increased Charlson Comorbidity Index (>2) was associated with local recurrence (P=0.049) (Table 4). Systemic recurrence was associated with perineural invasion (PNI; P<0.001), lymphovascular invasion (LVI; P=0.002), pN+ (P=0.001), advanced pT (≥3; P=0.003), CRM+ (P=0.014), and anastomotic leakage (P=0.014). Notably, tumor budding (TB) or poorly differentiated cluster (PDC) independently increased the rate of systemic recurrence (odds ratio [OR], 4.892; P=0.045) (Table 4). Additional excision of PME and TME did not affect either the local or systemic recurrence rate (P>0.999). The 5-year cumulative local (3.0% [P=0.445] to 5.1% [P>0.999]) and systemic recurrence rates (8.5% [P=0.112] to 17.2% [P=0.865]) did not differ by the DRMs, classified by cutoffs of 2, 3, and 4 cm, in all patients with middle/upper rectal cancer, regardless of pStages (0–II [P=0.397] vs. III–IV [P=0.899]) (Table 5).
Cumulative survival outcomes in the propensity score–matched PME and TME groups
Cumulative survival outcomes in the propensity score–matched PME and TME groups
Survival outcomes of propensity score–matched patients are shown in Table 3 and Fig. 3. The 5-year cumulative DFS (P=0.733) and OS (P=0.652) were similar in patients with middle/upper rectal cancer who underwent PME and TME, as were the 5-year DFS (81.4% vs. 74.0%, P=0.537) and OS (88.0% vs. 81.1%, P=0.847) in patients with middle rectal cancer. PNI independently reduced both DFS (hazard ratio [HR], 2.976; P=0.008) and OS (HR, 3.25; P=0.002) (Table 6). Anastomotic leakage (HR, 16.483; P=0.001) and unfavorable differentiation (poorly differentiated, mucinous, or signet-ring cell; HR, 2.936; P<0.050) were independently associated with reduced DFS, whereas inappropriate TME (HR, 2.839; P<0.050) and older age (>mean; HR, 2.144; P=0.010) were independently associated with reduced OS. Increased Charlson Comorbidity Index, CRM+, and pN+ were correlated with reduced DFS (P<0.050). The 5-year cumulative DFS and OS rates were not affected by DRM cutoffs, as were found in recurrence outcomes (Table 5).
Anorectal functional changes in the propensity score–matched PME and TME groups
Anorectal functional changes in the propensity score–matched PME and TME groups
Fecal Incontinence Score and principal manometric measurements did not differ between the PME and TME groups, except that MTV was lower in the TME than in the PME group until 6 to 12 months (P=0.004), and UDV was lower in the TME group until 12 to 24 months (P=0.045) (Fig. 4). In both groups, incontinence scores were higher at 12 to 24 months than at 6 to 12 months (6.6 vs. 3.7, P<0.001). Principal manometry values were also lower postoperatively than preoperatively (P<0.001), except for MSP (P=0.086), but all postoperative values were within the IQR of the healthy population [13]. Possible parameters associated with anorectal dysfunction were examined 12 to 24 months after surgery in middle/upper rectal cancer (Table 7). Incontinence was independently associated with TME (OR, 2.009; P<0.050), older age (OR, 4.366; P<0.001), and prolonged operation time (OR, 2.196; P<0.050). Reduced MRP and MSP were associated with older age and female sex, respectively (both P<0.001), while UDV and MTV were associated with prolonged operation time and tumor location in the middle rectum, respectively (both P<0.040).
DISCUSSION
DISCUSSION
Recurrence and survival rates in patients with middle/upper rectal cancer did not differ between those who underwent PME and TME in this study, confirming equivalent prognostic outcomes of the 2 procedures. Prognostic outcomes were consistent with a previous study involving 147 patients who underwent PME alone and the other review [4, 5]. Although the present study found that local recurrence rates in patients with middle rectal cancer were somewhat higher in the TME than in the PME group, the differences were not statistically significant. However, the systemic recurrence rate was significantly higher in the TME group. Few oncologically unfavorable parameters were observed in the TME group, except for greater tendency of anastomotic stricture and high rate of general morbidity [14]. Because the present study found that local recurrence was a potent predictor (5-folds) of systemic recurrence, a slightly higher local recurrence rate may be arithmetically amplified to yield a higher systemic recurrence rate in the TME group. On the other hand, type I error may somewhat affect an exaggerated difference in systemic recurrence rates between the 2 groups. These recurrence outcomes were not translated into any survival differences between the 2 procedures.
Biological traits of tumor deposits have been variably designated, for example, either tumor deposits (N1c) or mesorectal tumor microfoci [15]. These deposits are indicative of oncological aggressiveness, causing local recurrence and poorer prognosis, suggesting that these components can be combined into a unified category as ATDs. Thus, LVI/PNI, TB/PDC, extramural vascular invasion, and extranodal extension can be regarded as ATDs, based on their histological characteristics and biological behavior [16–21]. Systemic recurrence has been associated with PNI, LVI, and especially with TB/PDC in the present study. TB and PDC are regarded as powerful predictors of survival outcomes, outperforming the AJCC stage and other adverse features [18]. LVI and PNI are predictors of metastatic disease and recurrence with reduced survival, and have therefore been designated as category I prognostic indicators in the AJCC cancer staging. Inappropriate TME resulted in an HR of 2.8 for OS, in agreement with a previous Dutch TME trial [22] and a Norwegian audit [23]. All these findings emphasize the importance of en bloc excision with mesorectal fascia to achieve complete mesorectal excision, eliminating a substantial part of ATDs.
In this study, systemic recurrence was associated with CRM+ and advanced pT or pN+, whereas CRM+ and pN+ were correlated with reduced DFS. In line with these findings, showing that CRM+ correlated with systemic recurrence or DFS, 1 study suggested that CRM involvement is an indicator of advanced disease rather than inadequate local surgery because CRM+ patients die of distant disease before local recurrence [24]. Practically, the risk of CRM+ increases with more advanced T and N categories, making CRM+ a powerful predictor of distant metastases and reduced survival [3, 25]. The present study also found that unfavorable histology was an independent factor reducing DFS, in line with previous studies [26, 27]. Older age (>mean) independently correlated with reduced OS (HR, 2.144), whereas increased Charlson Comorbidity Index (>2) was associated with increased local recurrence and reduced DFS. These 2 parameters seem closely correlated with reduced survival, such that elderly patients with rectal cancer are at higher risk of treatment-related complications and comorbidities [28, 29].
Although this study did not evaluate measurable advantages of robot procedure, mechanistic advantages facilitate complete mesorectal excision, particularly for accurate mesofascial dissection preserving rectal and pelvic neurovascular bundles. Additionally, the robotic vessel sealer efficiently provides a circular and smooth cut surface of the distal mesorectum through effective hemostasis and clear amputation. Distal mesorectal excision must be accurately performed to secure a smooth mesorectal cut surface perpendicular to the rectal wall because an irregular mesorectal end can result in a severe mesorectal defect or insufficient bulk. The lack of correlation between additional excision and recurrence rate in the present study needs to be interpreted with caution, as only patients with advanced pT4 tumors underwent additional excision. Compared with a less extensive operation, more extensive surgery has been found to reduce the risk of recurrence in patients with advanced tumors [30].
Because TME has been associated with increased rates of anastomotic complications and anorectal dysfunction, PME according to tumor level is regarded as a reasonable surgical approach [3, 5, 6, 8]. Similarly, the present study found that incontinence was independently associated with TME (OR, 2.009) compared with PME, along with older age and prolonged operation time. Notably, the total length of the resected specimen and lymph node harvest did not differ significantly between patients who underwent PME and TME, suggesting equivalent oncological resection. Prognostic outcomes did not differ among the 3 levels of DRM (2, 3, and 4 cm) regardless of pStages, in accordance with previous findings, and recently the American Society of Colon and Rectal Surgeons (ASCRS) recommended a distal mural resection margin of 2 cm in their current guideline [3, 30, 31]. Although initial studies exhibited 4 to 5 cm distal mesorectal spread [8] which had been shown as intramural spread deposits from approximately 3 to 4 cm of the primary tumor, taken together, the present results indicate that PME may be an optimal choice for patients with middle rectal cancer with a lower margin of >5 cm from the anal verge, maintaining a DRM of 2 to 4 cm, except for tumors with unfavorable histology, high-risk mesorectal fascia, and pT4b or pN2 [12, 30, 32].
This study had several limitations. First, it was a retrospective, single-center, case-series analysis, suggesting a possible selection bias caused by customary implementation of PME or TME, with surgical procedure not chosen by absolute indication for middle rectal cancer. We attempted to minimize bias by reexamination of visual records and by propensity score matching using multivariate analyses. Second, comparative groups could not be perfectly propensity score–matched for recurrence and survival analyses, due to limited subjects of single institutional study. However, parameters potently associated with prognostic outcomes, namely, clinical stage and neoadjuvant treatment, were primarily matched to compare the PME and TME groups.
In conclusion, the findings of this study suggest that complete PME may be objectively valid in the treatment of middle rectal cancer based on oncological and functional outcomes. PME for middle rectal cancer can result in competent prognostic outcomes and lower morbidity rates, including lower rates of anastomotic complications and anorectal dysfunction. Although TME may sometimes induce intractable complications or anorectal dysfunction, it can alternatively be chosen for tumors with a lower margin of ≤5 cm from the anal verge, particularly in advanced T4 or N2 category and extensive ATDs. Randomized control trials comparing PME and TME in a sufficient number may confirm findings optimizing the use of PME in treating middle rectal cancer.
Footnotes

Conflict of interest

In Ja Park is the current Editor-in-Chief of Annals of Coloproctology; however, she did not interfere with the reviewing or decision process of this manuscript. No other potential conflict of interest relevant to this article was reported.

Funding

None.

Author contributions

Conceptualization: EJK, CWK, JCK; Data curation: all authors; Formal analysis: EJK, CWK, JLL, YSY; Investigation: EJK, CWK, JCK; Methodology: EJK, CWK, YSY, IJP, JCK; Project administra­tion: EJK, CWK, JCK; Resources: JCK, JLL; Validation: EJK, CWK, JLL, YSY, IJP, SBL, CSY; Writing–original draft: EJK, CWK, JCK; Writing–review & editing: all authors. All authors read and approved the final manuscript.

Fig. 1.
Flowchart of the study protocol. R0, curative resection with microscopically margin-negative resection; LR, lower rectum (≤5 cm from the anal verge); FAP, familial adenomatous polyposis; AFAP, attenuated FAP; LS, Lynch syndrome; MR, middle rectum (>5–10 cm from the anal verge); UR, upper rectum (>10–15 cm from the anal verge); PME, partial mesorectal excision; TME, total mesorectal excision; PSM, propensity score matching.
ac-2022-00689-0098f1.tif
Fig. 2.
Total mesorectal excision and related pelvic fascial structure. (A) Anterior and anterolateral pelvic cavity. (B) Posterior pelvic cavity. The area inside an ellipse indicates the total mesorectal excision dissection plane between the proper rectal and prehypogastric fascia, shown as a pasteboard-like fusion. HGN, hypogastric nerve.
ac-2022-00689-0098f2.tif
Fig. 3.
Cumulative 5-year (A–C) disease-free survival (DFS) and (D–F) overall survival (OS) rates in propensity score matching. (A, D) Patients with middle rectum (MR; >5–10 cm from the anal verge) cancer undergoing partial mesorectal excision (PME) or total mesorectal excision (TME). (B, E) Patients with MR and UR cancer undergoing PME or TME. (C, F) Patients with MR versus UR cancer.
ac-2022-00689-0098f3.tif
Fig. 4.
Anorectal function measurement at baseline (preoperative), 6 to 12 months, and >12 to 24 months after surgery in the partial mesorectal excision (PME) and total mesorectal excision (TME) groups. (A) Fecal Incontinence Score (FIS; the sum of solid, liquid, gas, pad use, and lifestyle alteration). (B) Lifestyle alteration. Four principal manometric parameters: (C) mean resting pressure (MRP), (D) maximal squeezing pressure (MSP), (E) urge to defecate volume (UDV), (F) maximal tolerance volume (MTV). Periods 0, 1, and 2 indicate values (mean±standard error of mean) at baseline, 6 to 12 months, and >12 to 24 months, respectively, concurrent with P0P1, showing P-values for comparisons between PME period 0 versus 1, equally applied for TME. Each bar shows the mean±standard deviation. Bold font, P>0.001; plain font, P=0.001 to P=0.05.
ac-2022-00689-0098f4.tif
Table 1.
Clinicopathological and operative parameters in patients who underwent PME or TME before and after propensity score matchinga
Parameter Before matching After matching
PME (n=437) TME (n=234) P-valueb D-valuec PME (n=115) TME (n=115) P-valueb D-valuec
Sex 0.934 0.014 >0.999 0
 Male 266 (60.9) 141 (60.3) 71 (61.7) 71 (61.7)
 Female 171 (39.1) 93 (39.7) 44 (38.3) 44 (38.3)
Age (yr) 59±10 59±11 0.168 0.129 58±10 58±9 >0.999 0
Tumor location (cm) 9.5±2.1 7.3±1.5 <0.001 NA 8.5±1.9 8.0±1.7 0.059 NA
 Middle rectum (>5–10 cm from AV) 137 (31.4) 179 (76.5) <0.001 0.083 63 (57.8) 63 (57.8) >0.999 0
 Upper rectum (>10–15 cm from AV) 300 (68.6) 55 (23.5) 52 (45.2) 52 (45.2)
cStage 0.019 0.235 >0.999 0
 0 5 (1.1) 2 (0.9) 4 (3.5) 1 (0.9)
 I 96 (22.0) 29 (12.4) 27 (23.5) 22 (19.1)
 II 50 (11.4) 29 (12.4) 7 (6.1) 15 (13.0)
 III 268 (61.3) 154 (65.8) 70 (60.9) 67 (58.3)
 IV 18 (4.1) 20 (8.5) 7 (6.1) 10 (8.7)
Neoadjuvant treatment+ 11 (2.5) 34 (14.5) <0.001 1.039 1 (0.9) 1 (0.9) >0.999 0
 AJCC/CAP TRG >0.999 0.282 >0.999 NA
  0 1 (9.1) 5 (14.7) 0 (0) 0 (0)
  1 2 (18.2) 5 (14.7) 0 (0) 0 (0)
  2 8 (72.7) 20 (58.8) 1 (100) 1 (100)
  3 0 (0) 5 (14.7) 0 (0) 0 (0)
Tumor direction (anterior) 166 (38) 106 (45.3) 0.070 0.166 38 (33.0) 47 (40.9) 0.274 0.186
Tumor long diameter (cm) 39±21 40±21 0.808 0.023 46±20 43±21 0.410 0.224
pStage 0.030 0.202 0.224 0.197
 0 12 (2.8) 6 (2.7) 4 (3.5) 1 (0.9)
 I 117 (27.7) 49 (22.1) 36 (31.9) 26 (23.9)
 II 122 (28.9) 57 (25.7) 28 (24.8) 29 (26.6)
 III 149 (35.3) 97 (43.7) 37 (32.7) 47 (43.1)
 IV 22 (5.2) 13 (5.9) 8 (7.1) 6 (5.5)
ASA PS classification (>II) 12 (2.7) 10 (4.3) 0.363 0.253 5 (4.3) 4 (3.5) >0.999 0.128
CCI (>2) 19 (4.3) 12 (5.1) 0.701 0.096 5 (4.3) 3 (2.6) 0.722 0.292
Body mass index (kg/m2) 24±3.2 23.6±3 0.871 0.261 23.9±3 23.6±3.2 0.792 0.058
Interspinous diameter (cm) 96±15 96±14 0.518 0.059 96±15 96±14 0.356 0.154
Midsagittal diameter (cm) 100±12 100±11 0.935 0.014 100±12 100±11 0.598 0.096
s-CEA (>6 ng/mL) 64 (14.6) 46 (19.7) 0.101 0.199 20 (17.4) 20 (17.4) >0.999 0
CRM+ 11 (2.5) 9 (3.8) 0.348 0.241 2 (1.7) 3 (2.6) >0.999 0.228
DRM (mm) 36±15 34±15 0.189 0.226 30±15 37±17 0.001 0.250
Growth 0.053 0.208 0.744 0.071
 Expanding 324 (77.9) 157 (70.7) 87 (77.7) 87 (79.8)
 Infiltrative 92 (22.1) 65 (29.3) 25 (22.3) 22 (20.2)
Tumor differentiation 0.059 0.399 >0.999 0.292
 Well-differentiated 53 (12.1) 29 (12.4) 16 (13.9) 12 (16.4)
 Moderately differentiated 368 (84.2) 188 (80.3) 96 (83.5) 98 (85.2)
 Poorly differentiated 6 (1.4) 9 (3.8) 2 (1.7) 2 (1.7)
 Mucinous adenocarcinoma 8 (1.8) 7 (3.0) 1 (0.9) 2 (1.7)
 Signet-ring cell 2 (0.5) 1 (0.4) 0 (0) 1 (0.9)
Lymphovascular invasion+ 143 (32.7) 80 (34.2) 0.731 0.036 39 (33.9) 40 (34.8) >0.999 0.021
Perineural invasion+ 93 (21.3) 60 (25.6) 0.210 0.134 19 (16.5) 30 (26.1) 0.107 0.319
TB+ or PDC+ 76 (24.6) 46 (25.4) 0.914 0.024 18 (23.4) 28 (30.1) 0.387 0.190
Complete TME+ 403 (92.2) 214 (91.5) 0.766 0.056 109 (94.8) 109 (94.8) >0.999 0
Total operative time (min) 164±51 182±54 <0.001 0.450 172±62 177±50 0.069 0.133
Multiple linear stapling (≥2×) 39 (8.9) 45 (19.6) <0.001 0.499 11 (9.6) 22 (19.3) 0.059 0.444
Transient ileal diversion+ 52 (11.9) 84 (36.5) <0.001 0.625 14 (12.2) 36 (31.6) 0.001 0.658
Surgical complication+ 61 (14.5) 48 (21.4) 0.027 0.264 17 (14.8) 20 (18.3) 0.590 0.131
 Clavien-Dindo grade (≥III) 21 (4.8) 21 (9.0) 0.331 0.217 3 (17.6) 8 (40.0) 0.169 0.626
 Anastomotic leakage+ 11 (2.5) 10 (4.3) 0.246 0.302 1 (0.9) 2 (1.7) >0.999 0.387
 Anastomotic stricture+ 2 (0.5) 5 (2.1) 0.054 0.859 1 (0.9) 2 (1.7) >0.999 0.387
 Permanent diversion+ 0 (0) 6 (2.6) 0.002 Infinity 0 (0) 3 (2.6) 0.247 Infinity
Chemotherapy+ (HRM or pStage ≥III) 165/209 (78.9) 101/132 (76.5) 0.595 0.078 45/55 (81.8) 46/60 (76.7) 0.447 0.173
Extra-analgesicsd (>4 times) 119 (27.2) 60 (25.6) 0.714 0.047 32 (27.8) 22 (19.1) 0.161 0.269
Flatus passage (day) 2.2±0.9 2.1±1.0 0.798 0.028 2.1±0.8 2.1±0.9 0.779 0.066
Hospitalization (day) 7.1±2.5 8.3±3.5 <0.001 0.601 7±1.6 8.1±2.8 0.007 0.471

Values are presented as number (%), mean±standard deviation, or number only.

PME, partial mesorectal excision; TME, total mesorectal excision; NA, not applicable; AV, anal verge; cStage, clinical staging; AJCC, American Joint Committee of Cancer; CAP, College of American Pathologists; TRG, tumor regression grade; pStage, pathologic staging; ASA, American Society of Anesthesiologists; PS, physical status; CCI, Charlson Comorbidity Index; s-CEA, preoperative level of serum carcinoembryonic antigen; CRM, circumferential resection margin; DRM, distal resection margin; TB, tumor budding; PDC, poorly differentiated cluster; HRM, high-risk mesorectal fascia (threatened or involved mesorectal fascia and suspicious invasion into the adjacent viscera).

aAdjusted for sex, mean age, neoadjuvant treatment, and cStage between the PME and TME groups. bCategorical parameters were compared by 2-sided Fisher exact test and continuous parameters by Student t-test. cThe D-value indicates a standard difference expressed as log odds ratio multiplied by 1.814. Values expressed as quantities were analyzed using 2-by-2 frequency tables with means as cutoff points to divide values into 2 levels. dFrequency of nonsteroidal anti-inflammatory drugs, regardless of percutaneous analgesic device.

Table 2.
Characteristics of patients with MR (>5–10 cm from AV) or UR (>10–15 cm from AV) cancer who underwent PME or TME before and after propensity score matchinga
Parameter Before matching After matching
No. of patients P-valueb D-valuec No. of patients P-valueb D-valuec
PME TME PME TME
Patients with MR cancer who underwent PME vs. TME, elapsed 5 yr after R0 resection 93 107 - - 79 79 - -
 Sex 0.884 0.022 0.746 0.087
  Male 58 65 46 49
  Female 35 42 33 30
 Age (mean, 58 yr) 0.261 0.179 0.055 0.370
  <Mean 51 50 37 50
  ≥Mean 42 57 42 29
 cStaged 0.033 0.402 0.570 0.159
  0–II 30 20 16 20
  III 63 87 63 59
 Neoadjuvant treatment 0.028 0.624 0.101 0.612
  – 89 92 75 68
  + 4 15 4 11
Patients with MR and UR cancer who underwent PME vs. TME, elapsed 5 yr after R0 resection 273 123 - - 94 94 - -
 Sex >0.999 0.008 0.374 0.170
  Male 170 77 59 52
  Female 103 46 35 42
 Age (mean, 58 yr) 0.515 0.088 >0.999 0
  <Mean 144 60 50 50
  ≥Mean 129 63 44 44
 cStaged 0.131 0.236 >0.999 0
  0–II 74 24 23 23
  III 199 99 71 71
 Tumor location <0.001 1.412 >0.999 0
  MR (>5–10 cm from AV) 93 107 78 78
  UR (>10–15 cm from AV) 180 16 16 16
 Neoadjuvant treatment 0.001 0.815 >0.999 0
  – 264 107 93 93
  + 9 16 1 1
Patients with MR vs. UR cancer who elapsed 5 yr after R0 resectione 200 196 - - 109 109 - -
 Sex 0.756 0.042 <0.001 0.623
  Male 123 124 70 40
  Female 77 72 39 69
 Age (mean, 58 yr) 0.689 0.045 0.786 0.061
  <Mean 101 10 59 56
  ≥Mean 99 93 50 53
 cStaged 0.908 0.015 0.069 0.304
  0–II 50 48 34 48
  III 150 148 75 61
 Neoadjuvant treatment 0.012 0.662 >0.999 0.106
  – 181 190 104 103
  + 19 6 5 16
 Excision type <0.001 1.412 >0.999 0.039
  PME 93 180 92 93
  TME 107 16 17 16
Patients with MR cancer who underwent PME vs. TME, elapsed 12–24 mo after R0 resection (pStaged ≤III and age ≤65 yr)e 304 141 - - 106 106 - -
 Sex 0.400 0.099 >0.999 0.022
  Male 196 85 66 67
  Female 108 56 40 39
 Age (mean, 58 yr) 0.541 0.077 0.784 0.062
  <Mean 155 67 52 55
  ≥Mean 149 74 54 51
 cStaged 0.223 0.160 0.651 0.101
  0–II 98 37 29 33
  III 206 104 77 73
 Tumor location <0.001 1.199 >0.999 0.025
  MR (>5–10 cm from AV) 90 111 75 76
  UR (>10–15 cm from AV) 214 30 31 30
 Neoadjuvant treatment <0.001 1.094 >0.999 0.387
  – 298 123 104 105
  + 6 18 2 1

MR, middle rectum; AV, anal verge; UR, upper rectum; PME, partial mesorectal excision; TME, total mesorectal excision; cStage, clinical staging; pStage, pathologic staging; AJCC, American Joint Committee on Cancer.

aAdjusted for sex, mean age, (tumor location, PME/TME), and cStage. bCategorical parameters are compared by 2-sided Fisher exact test. cThe D-value indicates a standard difference expressed as log odds ratio multiplied by 1.814. Value expressed as quantities were analyzed using 2-by-2 frequency tables with means as cutoff points used to divide values into 2 levels. dAccording to AJCC Cancer Staging Manual 8th ed. eValues of this category are for MR and UR cancer, not PME and TME.

Table 3.
Comparison of prognostic outcomes in propensity score–matcheda patients with MR (>5–10 cm from AV) or UR (>10–15 cm from AV) cancer undergoing PME or TME
Parameter MR and UR MRb MR and UR
PME group (n=94) TME group (n=94) P-value PME group (n=79) TME group (n=79) P-value MR group (n=109) UR group (n=109) P-value
Local recurrence 5 (5.3) 4 (4.3) >0.999 4 (5.1) 7 (8.9) 0.534 5 (4.6) 1 (0.9) 0.212
Systemic recurrence 8 (8.5) 15 (16.0) 0.181 6 (7.6) 18 (22.8) 0.013 11 (10.1) 8 (7.3) 0.632
5-yr DFS (%) 81.2 81.7 0.733 81.4 74.0 0.537 81.8 88.7 0.142
5-yr OS (%) 88.9 86.0 0.652 88.0 81.1 0.847 89.4 91.4 0.423

Values are presented as number (%) or number only.

MR, middle rectum; AV, anal verge; UR, upper rectum; PME, partial mesorectal excision; TME, total mesorectal excision; DFS, disease-free survival; OS, overall survival; cStage, clinical staging; AJCC, American Joint Committee on Cancer.

aAdjusted for sex, mean age, cStage (according to AJCC Cancer Staging Manual 8th ed), tumor location, and neoadjuvant treatment between the PME and TME groups; sex, mean age, cStage, and neoadjuvant treatment between the PME and TME groups; sex, mean age, cStage, neoadjuvant treatment, and PME/TME between the middle and upper rectal cancer group. bDivided into 2 parts as upper (≥7 cm from AV, n=62) and lower half (<7 cm from AV, n=96).

Table 4.
Univariate and multivariate analyses of clinicopathological parameters associated with 5-year cumulative local and systemic recurrence in propensity score–matched patientsa with middle and upper rectal cancer undergoing PME (n=94) and TME (n=94)
Parameter 5-yr Cumulative local recurrence 5-yr Cumulative systemic recurrence
No. of events (%) P-valueb OR (95% CI) P-valuec No. of events (%) P-valueb OR (95% CI) P-valuec
CCI 0.049 0.294 (0.057–1.520) 0.144 >0.999 NA NA
 ≤2 7 (3.9) 22 (12.2)
 >2 2 (25.0) 1 (12.5)
Midsagittal diameter 0.080 1.254 (0.699–2.251) 0.448 >0.999 NA NA
 ≤Mean 8 (7.5) 13 (12.3)
 >Mean 1 (1.2) 10 (12.2)
Excision type >0.999 NA NA 0.181 NA NA
 PME 5 (5.3) 8 (8.5)
 TME 4 (4.3) 15 (16.0)
TME 0.137 NA NA 0.386 NA NA
 Complete 7 (4.0) 20 (11.5)
 Inappropriated 2 (14.3) 3 (21.4)
Multiple stapling >0.999 NA NA 0.091 0.910 (0.145–5.708) 0.920
 ≤2 7 (4.8) 15 (10.2)
 >2 2 (5.4) 8 (21.6)
DRM 0.483 NA NA >0.999 NA NA
 ≤1 cm 1 (7.7) 1 (7.7)
 >1 cm 8 (4.6) 22 (12.6)
CRM 0.904 NA NA 0.014 4.81×106 (0–infinity) >0.999
 – 8 (4.3) 21 (11.3)
 + 1 (50.0) 2 (100)
Pathological T categorye 0.081 1.445 (0.802–2.605) 0.220 0.003 2.693 (0.426–17.022) 0.292
 0–2 1 (1.3) 3 (3.8)
 3–4 8 (7.4) 20 (18.5)
Pathological N categorye 0.166 NA NA 0.001 1.040 (0.181–5.958) 0.965
 – 3 (2.7) 6 (5.5)
 + 6 (7.7) 17 (21.8)
Tumor differentiation 0.090 1.201 (0.334–4.326) 0.779 0.137 NA NA
 Well or moderately differentiated 7 (4.0) 20 (27.3)
 Poorly differentiated, MAC, or SRC 2 (18.2) 3 (27.3)
LVI 0.499 NA NA 0.002 1.989 (0.457–8.655) 0.360
 – 5 (4.1) 8 (6.5)
 + 4 (6.2) 15 (23.1)
PNI 0.195 NA NA <0.001 4.492 (0.953–21.164) 0.057
 – 6 (3.9) 11 (7.1)
 + 3 (9.1) 12 (36.4)
TB or PDC 0.582 NA NA 0.068 4.892 (1.035–23.133) 0.045
 – 5 (5.3) 8 (8.4)
 + 0 (0) 5 (22.7)
Anastomotic leakage >0.999 NA NA 0.014 1.08 × 107 (0) >0.999
 – 9 (4.8) 21 (11.3)
 + 0 (0) 2 (100)
Anastomotic stricture 0.094 0.889 (0.051–15.474) 0.936 0.230 NA NA
 – 8 (4.3) 22 (11.8)
 + 1 (50.0) 1 (50.0)

PME, partial mesorectal excision; TME, total mesorectal excision; OR, odds ratio; CI, confidence interval; CCI, Charlson Comorbidity Index; NA, not applicable; DRM, distal resection margin; CRM, circumferential resection margin; MAC, mucinous adenocarcinoma; SRC, signet-ring cell; LVI, lymphovascular invasion; PNI, perineural invasion; TB, tumor budding; PDC, poorly differentiated cluster; cStage, clinical staging; AJCC, American American Joint Committee on Cancer.

aAdjusted for sex, mean age, neoadjuvant treatment, tumor location, and cStage (0–II vs. III–IV, according to AJCC Cancer Staging Manual 8th ed). bCategorical parameters were compared by 2-sided Fisher exact test. cPotential parameters were verified using binary logistic regression. dIncluding near-complete and incomplete. eAccording to AJCC Cancer Staging Manual 8th ed.

Table 5.
Prognostic outcomes 5 years after R0 resection as a function of respective distal resection margins in all patients with MR (>5–10 cm from AV) or UR (>10–15 cm from AV) cancer
Parameter Distal resection margin (cm)a
≤2 (n=82) >2 (n=314) P-value ≤3 (n=198) >3 (n=198) P-value ≤4 (n=303) >4 (n=93) P-value
Local recurrence 3 (3.7) 13 (4.1) >0.999 10 (5.1) 6 (3.0) 0.445 13 (4.3) 3 (3.2) 0.772
Systemic recurrence 7 (8.5) 49 (15.6) 0.112 22 (11.1) 34 (17.2) 0.112 44 (14.5) 12 (12.9) 0.865
5-yr DFS (%) 84.7 80.0 0.102 81.6 80.3 0.726 80.2 83.4 0.469
5-yr OS (%) 90.2 87.2 0.116 88.4 87.3 0.914 87.9 87.6 0.946

Values are presented as number (%) or number only.

MR, middle rectum; AV, anal verge; UR, upper rectum; DFS, disease-free survival; OS, overall survival; pStage, pathologic staging; AJCC, American Joint Committee on Cancer.

aRespective distal resection margin category was not associated with pStage according to AJCC Cancer Staging Manual 8th ed; 2 cm, P=0.899; 3 cm, P=0.837; 4 cm, P=0.397.

Table 6.
Univariate and multivariate analyses of clinicopathological parameters associated with 5-year DFS and OS in propensity score–matched patientsa with middle and upper rectal cancer undergoing PME (n=94) and TME (n=94)
Parameter 5-yr Cumulative DFS 5-yr Cumulative OS
No. of events (%) P-valueb HR (95% CI) P-valuec No. of events (%) P-valueb HR (95% CI) P-valuec
Age (mean, 58 yr) 0.035 1.751 (0.893–3.433) 0.103 0.036 2.144 (1.015–4.526) 0.045
 ≤Mean 16 (16.0) 12 (12.0)
 >Mean 26 (29.5) 21 (23.9)
CCI 0.015 2.359 (0.700–7.956) 0.166 0.033 1.844 (0.496–6.859) 0.361
 ≤2 37 (20.6) 29 (16.1)
 >2 5 (62.5) 4 (50.0)
Excision 0.861 NA NA 0.702 NA NA
 PME 23 (23.4) 18 (19.1)
 TME 20 (21.3) 15 (16.0)
TME 0.170 NA NA 0.020 2.839 (1.008–7.996) 0.048
 Complete 36 (20.1) 27 (15.5)
 Inappropriated 7 (50.0) 6 (42.9)
Multiple stapling 0.129 NA NA 0.148 NA NA
 ≤2 30 (20.4) 23 (15.6)
 >2 12 (32.4) 10 (27.0)
Distal resection margin 0.736 NA NA 0.471 NA NA
 ≤1 cm 2 (15.4) 1 (7.7)
 >1 cm 40 (22.9) 32 (18.3)
Circumferential resection margin 0.049 3.792 (0.614–23.411) 0.151 0.321 NA NA
 – 40 (21.5) 32 (17.2)
 + 2 (100) 1 (50.0)
Pathological T categorye 0.051 1.490 (0.702–3.163) 0.151 0.126 NA NA
 0–2 12 (15.0) 10 (12.5)
 3–4 30 (27.8) 23 (21.3)
Pathological N categorye 0.022 0.979 (0.422–2.272) 0.96 0.120 NA NA
 – 18 (16.4) 15 (13.6)
 + 24 (30.8) 18 (23.1)
Tumor differentiation 0.070 2.936 (1.099–7.854) 0.032 0.105 NA NA
 Well or moderately differentiated 37 (20.9) 29 (16.4)
 Poorly differentiated, MAC, or SRC 5 (45.5) 4 (36.4)
Lymphovascular invasion 0.065 0.963 (0.430–2.157) 0.927 0.318 NA NA
 – 22 (17.9) 19 (15.4)
 + 20 (30.8) 14 (21.5)
Perineural invasion 0.001 2.976 (1.377–6.626) 0.008 0.004 3.250 (1.537–6.875) 0.002
 – 27 (17.4) 21 (13.5)
 + 15 (45.5) 12 (36.4)
TB or PDC >0.999 NA NA >0.999 NA NA
 – 21 (22.1) 16 (16.8)
 + 5 (22.7) 3 (13.6)
Anastomotic leakage 0.049 16.483 (3.222–84.319) 0.001 0.321 NA NA
 – 40 (21.5) 32 (17.2)
 + 2 (100) 1 (50.0)
Anastomotic stricture 0.398 NA NA >0.999 NA NA
 – 41 (22.0) 33 (17.7)
 + 1 (50.0) 0 (0)

DFS, disease-free survival; OS, overall survival; PME, partial mesorectal excision; TME, total mesorectal excision; HR, hazard ratio; CI, confidence interval; CCI, Charlson Comorbidity Index; NA, not applicable; MAC, mucinous adenocarcinoma; SRC, signet-ring cell; TB, tumor budding; PDC, poorly differentiated cluster; cStage, clinical staging; AJCC, American American Joint Committee on Cancer.

aAdjusted for sex, mean age, neoadjuvant treatment, tumor location, and cStage (0–II vs. III–IV, according to AJCC Cancer Staging Manual 8th ed). bCategorical parameters were compared by 2-sided Fisher exact tests. cPotential parameters were compared by Cox regression analyses using potential variables. dIncluding near-complete and incomplete. eAccording to AJCC Cancer Staging Manual 8th ed.

Table 7.
Clinicopathological features associated with anorectal dysfunction 12 to 24 months after PME and TME in propensity score–matched patientsa
Parameter FIS>mean (3.7)b MRP≤mean (41 mmHg) MSP≤mean (172 mmHg) UDV≤mean (57 mL) MTV≤mean (122 mL)
No. (%) P-valuec OR (95% CI) P-valued No. (%) P-valuec No. (%) P-valuec No. (%) P-valuec No. (%) P-valuec
Sex 0.524 NA NA 0.278 <0.001 0.111 0.205
 Male 40/109 (36.7) 59/102 (57.8) 68/126 (54.0) 22/102 (21.6) 73/102 (71.6)
 Female 22/69 (31.9) 34/69 (49.3) 63/75 (84.0) 23/69 (33.3) 56/69 (81.2)
Age (mean, 58 yr) <0.001 4.366 (2.173–8.775) <0.001 <0.001 0.768 0.607 0.156
 ≤Mean 19/93 (20.4) 39/93 (41.9) 64/100 (64.0) 36/93 (28.0) 66/93 (71.0)
 >Mean 43/85 (50.6) 54/78 (69.2) 67/101 (66.3) 19/78 (24.4) 63/78 (80.8)
Tumor location 0.118 NA NA 0.501 >0.999 0.458 >0.999
 Middle rectum 49/127 (38.6) 91/178 (53.6) 129/198 (65.2) 44/169 (26.0) 127/169 (75.1)
 Upper rectum 13/51 (5.5) 2/2 (100) 2/3 (66.7) 1/2 (50.0) 2/2 (100)
Neoadjuvant treatment 0.120 NA NA 0.502 0.102 >0.999 0.004
 – 60/176 (34.1) 68/121 (56.2) 99/144 (68.8) 32/121 (26.4) 99/121 (81.8)
 + 2/2 (100) 25/50 (50.0) 32/57 (56.1) 13/50 (26.0) 30/50 (60.0)
Excision 0.059 2.009 (1.015–3.975) 0.045 0.539 0.660 0.164 0.158
 PME 28/98 (28.6) 46/89 (51.7) 68/102 (66.7) 19/89 (21.3) 63/89 (70.8)
 TME 34/80 (42.5) 47/82 (57.3) 63/99 (63.6) 26/82 (31.7) 66/82 (80.5)
TME 0.280 NA NA 0.456 0.722 >0.999 >0.999
 Complete 57/169 (33.7) 88/164 (53.7) 126/192 (65.6) 43/165 (26.1) 123/165 (74.5)
 Incomplete 5/7 (71.4) 5/6 (83.3) 6/6 (100) 2/6 (33.3) 6/6 (100)
Tumor differentiation 0.051 4.8 (0.846–27.253) 0.077 0.221 0.094 0.654 0.338
 Well or moderately differentiated 57/171 (33.3) 88/165 (53.3) 125/195 (64.1) 43/165 (26.1) 123/165 (74.5)
 Poorly differentiated, MAC, or SRC 5/7 (71.4) 5/6 (83.3) 6/6 (100) 2/6 (33.3) 6/6 (100)
Operation time (mean, 95 min) 0.056 2.196 (1.052–4.581) 0.036 0.302 0.619 0.034 0.171
 ≤Mean 39/128 (30.5) 64/124 (51.6) 94/146 (64.4) 27/124 (21.8) 90/124 (72.6)
 >Mean 23/50 (46.0) 29/47 (61.7) 37/54 (68.5) 18/47 (38.3) 39/47 (83.0)
Ileal diversion 0.539 NA NA 0.686 0.439 0.038 >0.999
 – 19/32 (59.4) NA NA 31/139 (22.3) NA
 + 13/32 (40.6) NA NA 12/29 (41.4) NA

PME, partial mesorectal excision; TME, total mesorectal excision; FIS, Fecal Incontinence Score; MRP, mean resting pressure; MSP, maximal squeezing pressure; UDV, urge to defecate volume; MTV, maximal tolerance volume; OR, odds ratio; CI, confidence interval; NA, not applicable; AV, anal verge; MAC, mucinous adenocarcinoma; SRC, signet-ring cell; AJCC, American Joint Committee on Cancer; No., (+) No./Evaluated No.

aAdjusted for sex, mean age, clinical staging (according to AJCC Cancer Staging Manual 8th ed), tumor location, and neoadjuvant treatment. bAssessed by Wexner FIS (https://www.mdcalc.com/wexner-score-obstructed-defecation-syndrome-ods). cCategorical parameters were compared by 2-sided Fisher exact tests. dPotentially associated parameters were compared by logistic regression analysis.

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