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Lymph-node metastasis is considered as critical prognostic factor in colorectal cancer. A preoperative evaluation of lymph-node metastasis can also help to determine the range of distant lymph node dissection. However, the reliability of 18F-fluorodeoxyglucose positron emission tomography/computed tomography (FDG-PET/CT) in the detection of lymph-node metastasis is not fully known.
The medical records of 433 patients diagnosed with colorectal cancer were reviewed retrospectively. FDG-PET/CT and CT were performed on all patients. Lymph nodes were classified into regional and distant lymph nodes according to the American Joint Committee on Cancer (AJCC) Cancer Staging Manual, 7th edition.
The patients included 231 males (53.3%) and 202 females (46.7%), with a mean age of 64.7 ± 19.0 years. For regional lymph nodes, the sensitivity of FDG-PET/CT was lower than that of CT (57.1% vs. 73.5%, P < 0.001). For distant lymph nodes, the sensitivity of FDG-PET/CT was higher than that of CT (64.7% vs. 52.9%, P = 0.012). The sensitivity of FDG-PET/CT for regional lymph nodes was higher in patients with larger primary tumors. The positivity of lymph-node metastasis for FDG-PET/CT was affected by carcinoembryonic antigen levels, tumor location, and cancer stage for regional lymph nodes and by age and cancer stage for distant lymph nodes (P < 0.05).
The sensitivity of FDG-PET/CT for regional lymph-node metastasis was not superior to that of CT. However, FDG-PET/CT provides helpful information for determining surgical plan especially in high risk patients group.
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The carcinoid tumor was recently categorized as a malignant disease due to its possibility of metastasis. This study was aimed to investigate the clinical characteristics and the metastatic rate of colorectal carcinoid tumors.
Charts were reviewed for 502 patients diagnosed with and treated for colorectal carcinoid tumors between January 2006 and December 2009. The location, size, depth and metastatic status of the tumors were collected.
Including 24 synchronous tumors from 12 patients, 514 carcinoid tumors were removed. Most of them were found in the rectum (97.3%). The male-to-female ratio was 1.38 to 1, and mean age was 50.2 ± 11.4 years. The mean tumor size was 5.8 ± 3.6 mm. Less than 10-mm-sized tumors had a 1.95% lymph node metastatic rate; tumors with sizes from 10 mm to 20 mm and larger than 20 mm had 23.5% and 50% lymph node metastatic rates, respectively. Two cases had distant metastasis; one with a 22-mm-sized tumor metastasized to the liver, and the other with a 20-mm-sized tumor metastasized to the peritoneum. Among 414 patients who completed metastatic studies, 93.8% were classified as stage I, 0.9% as stage II, 4.8% as stage III and 0.5% as stage IV.
Colorectal carcinoid tumors smaller than 10 mm have a low rate of lymph node metastasis, but those sized 10 mm or larger incur significant risk. Further investigation regarding additional risk factors should be done to develop proper treatment guidelines for these tumors.
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