OBJECTIVETo study the incidence rate of multiple primary colorectal carcinomas (MPCC) in colorectal carcinoma and to evaluate its clinical and pathological characteristics.

METHODSOne hundred and sixty-eight (4.6%) patients from 3663 cases with colorectal carcinoma were diagnosed with MPCC from January 1985 to December 2003. The clinical data of the patients were collected retrospectively to investigate the diagnosis and treatment of MPCC.

RESULTSOf the 168 patients, 81 were diagnosed as synchronous colorectal carcinoma (SC), 72 with metachronous colorectal carcinoma (MC), 15 with both SC and MC. The median age at time of diagnosis of colorectal carcinoma was 58 years old (range from 20 to 82 years old). Three hundred and ninety-three cancer lesions were detected in these 168 cases (mean, 2.3 lesions/case). The rectum and sigmoid colon were the most involved sites (61.6%). Eighteen cases (10.7%) were verified with hereditary non-polyposis colorectal cancer (HNPCC) while another 9 cases were highly suspected. Fourteen patients (8.3%) were found with other malignancies out of large intestine, 41 patients (24.4%) with colorectal adenomas, 72 (42.9%) with adenoma carcinogenesis. Among the 96 SC patients, 91 were given preoperative colonoscopy and 65 (71.4%) got the diagnosis. All the MC patients were diagnosed by postoperative colonoscopy. The overall 5-year survival rate of the 168 patients was 69.8%.

CONCLUSIONSMPCC should be paid more attention in colorectal cancer management. Colonoscopic surveillance is much more important in diagnosis and follow-up of MPCC for reducing the misdiagnosis of SC and detecting more MC in time. Prompt treatment of adenoma can reduce the occurrence of MPCC, and active and standard surgical treatment should be done for MPCC.