Excess risk of subsequent primary cancers among colorectal carcinoma survivors, 1975-2001

BACKGROUND. Studies of persons with colorectal cancer have reported increased risk of subsequent primary cancers. Results have not been consistent, however, and there is little information about such risk in specific races and ethnic populations. METHODS. Using 1975-2001 data from the Surveillance, Epidemiology, and End Results (SEER) Program, we assembled 262,600 index cases of colorectal carcinoma to assess the occurrence of subsequent primary cancers in 13 noncolonic sites. Observed (0) subsequent cancers were compared with those expected (E) based on age-/sex-/race-/year-/site-specific rates in the SEER population. The standardized incidence ratio (SIR) and the absolute excess risk (AER) represent 'O divided by E' and 'O - E,' respectively. RESULTS. Colorectal carcinoma patients had significantly elevated SIRs for small gut, stomach (males), kidney, and corpus uteri cancers, ranging from 1.13 for stomach cancer in males to 3.45 for small gut cancer in females. Elevated SIRs for additional sites were seen in certain population subgroups: pancreas and ovary in persons aged < 50 years, and prostate in black males. The excess burden, as assessed by AER, was notable for prostate cancer in black males and for corpus uteri cancer in females aged < 50 years (26.5 and 9.5 cancers per 10,000 person-years, respectively), and it persisted beyond 5 years of follow-up. CONCLUSIONS. Although significantly elevated SIRs were found for several cancers, the excess burden was notable only for cancer of the prostate in black males and of the corpus uteri in females under age 50.