Background: Reports on the frequency of multiple carcinomas of the colon and rectum have varied from 3-4% to more than 10% of all tumors of the large bowel.
Methods: We reviewed the files of a specialized colorectal cancer registry with the following objectives: a) to determine the frequency of multiple tumors (synchronous or metachronous) in the general population; b) to compare these values with those observed in patients with hereditary nonpolyposis colorectal carcinoma (HNPCC); and c) to evaluate the clinical outcome of patients with multiple tumors and the role of other clinical parameters in the development of these neoplasms.
Results: From 1984 to 1992, 53 patients with multiple tumors (of 1298 registered patients, 4%) had large bowel carcinoma; 33 (2.5%) were synchronous and 20 (1.5%) metachronous. The total number of multiple colorectal carcinomas was 95, which was 7% of all registered colorectal carcinomas (1337 carcinomas in 1298 patients). Multiple tumors occurred significantly more often in patients with HNPCC than in those with sporadic carcinomas (P < 0.001); this increased prevalence was more marked for metachronous lesions, which occurred almost 4 times more often in patients with HNPCC (5.8% vs. 1.3%; P < 0.001). The average interval of time between the first and the second malignancy was 8.7 years; there was no significant difference between hereditary and sporadic tumors. Patients with synchronous tumors did not show appreciable differences in survival when compared with individuals who had single neoplasms. In contrast, a poor clinical outcome was observed in patients with metachronous tumors after the development of the second carcinoma. Finally, polypoid adenomas of the large bowel were found significantly more often in patients with multiple primary tumors than in those with a single tumor.
Conclusions: These results emphasize the importance of preoperative pancolonoscopy for the identification of possible synchronous tumors (both benign and malignant) and long-lasting endoscopic follow-up for the detection of recurrent or metachronous lesions. The conclusions are even more pertinent for patients with HNPCC, whose risk of metachronous tumors is significantly higher than that of patients with sporadic carcinoma.