Clinical characteristics of metachronous colorectal tumors.

A cancer-registry-based study was conducted to investigate the survival patterns associated with metachronous colorectal tumors and to compare the survival of patients with single and metachronous colorectal tumors. The study included all 1,396 White patients with metachronous colorectal tumors diagnosed among 143,283 patients with primary colorectal tumors reported between 1973-1986 to the SEER program. The influence on survival of age at diagnosis, site of tumor and stage was evaluated by means of multivariate survival analysis, using Cox Proportional Hazards Models. Metachronous tumors developed more often following left-colon tumors. Stage distribution of the second tumors was better than that of single 47% of the second tumors were discovered in regionally-advanced or distant-metastatic stages. Survival from the second tumor diagnosed in the rectum was worse than that of a single tumor in the same stage and site. Only the stage of the second tumor was found to influence survival from metachronous tumors. The relatively high rate of diagnosis of advanced second colorectal tumors may reflect either improper follow-up after the diagnosis of the first tumor, or more aggressive biological characteristics of the second tumors.