Incidence and survival of mucinous adenocarcinoma of the colorectum: a population-based study from an Asian country.

PURPOSE: Previous studies have shown conflicting results on the prognosis of mucinous adenocarcinoma of the colorectum. This could be because of heavy bias on patient selection. Furthermore, little data are available from Asian populations. This study was designed to examine incident and prognostic characteristics of mucinous adenocarcinoma of the colorectum based on data obtained from a population-based, Asian, cancer registry.
METHODS: A total of 627 of 15,762 were mucinous adenocarcinoma cases from invasive colorectal cancer patients registered in the Singapore Registry from 1968 to 1997. Age-standardized incidence rate was used to describe the incident pattern of mucinous adenocarcinoma of colon and rectum during a period of time. Survival of patients with mucinous adenocarcinoma or ordinary adenocarcinoma was compared using relative survival and proportional hazards model.
RESULTS: Age-standardized incidence rate of mucinous adenocarcinoma of the colon and rectum were almost unchanged in males, rising slightly in females during the study periods from 1968 to 1972 to 1993 to 1997. The proportion of mucinous adenocarcinoma cases was similar among genders and calendar-year periods but was higher in younger age groups, Malays and Indians, in advanced stages of the disease, and proximal colon. Five-year relative survival rate of patients with mucinous adenocarcinoma were similar in the colon but were lower in the rectum.
CONCLUSIONS: Colorectal mucinous adenocarcinoma as a different etiologic entity from other histologic types of colorectal cancer was suggested. Possibly greater aggressiveness of mucinous adenocarcinoma occurring in the rectum requires confirmation but suggests that mucin is important in the pathogenesis of mucinous adenocarcinoma.