The importance of tumor stage and relative survival analysis for the association between sex and survival after resection of colorectal cancer.

OBJECTIVE: The aim of this study was to determine whether the previously noted poorer survival of men after resection of colorectal cancer varied among clinicopathological tumor stages. SUMMARY BACKGROUND DATA: The question of whether sex is independently associated with prognosis after resection of colorectal cancer has been examined in numerous studies over the past 2 decades, but with conflicting results.
METHODS: Data on 3,301 patients were drawn from a comprehensive, prospective hospital registry of all resections for colorectal cancer performed between January 1971 and December 2005. Statistical analysis employed Kaplan Meier estimation and relative survival analysis to adjust for differential male/female life expectancy in the general population.
RESULTS: The relative survival of males was significantly less than that of females (P = 0.004) only in stage B. This was not accounted for by other negative pathology features and cause of death did not differ significantly between males and females. However, men with stage B tumor were more likely than women to experience postoperative morbidity, particularly a respiratory complication or a surgical complication requiring urgent reoperation. The sex difference in relative survival persisted among patients who had either a respiratory complication or an urgent reoperation (P = 0.003) but disappeared among those who had neither (P = 0.193).
CONCLUSION: The poorer survival of men with stage B tumor was attributable to their greater postoperative morbidity which led to the earlier death of some due to causes unrelated to their colorectal cancer.