Risk of colorectal cancer among long-term cervical cancer survivors.

Because advances in therapy have increased long-term survival for women with cervical cancer, it is important to study the risk of secondary primary malignancies in high-dose organ areas. From the 1973-2009 National Cancer Institute Surveillance, Epidemiology, and End Results (SEER) program, we studied the risk of developing cancer of the colon and rectum in 64,507 cervical cancer patients over 35 years after initial radiation treatment. We also assessed change in risk over time. Kaplan-Meier estimator for survival curve and Cox proportional hazards models was used. More than half (52.6%) of the cervical cancer patients received radiation treatment. In the analyses adjusted for race/ethnicity, age, marital status, surgery status, stage and grade, the risk of colon cancer between those both with and without XRT diverged beginning at approximately 8 years. After 8 years, the hazard ratio for developing colon cancer was 2.00 (95% CI 1.43-2.80) for women with radiation versus those without radiation treatment. The risk of rectal cancer diverged after 15 years of follow-up (HR 4.04, 95% CI 2.08-7.86). After 35 years of follow-up, the absolute risk of developing colon cancer was 6.5% for those who received radiation versus 2.5% for those without, and 3.7 versus 0.8% for rectum. The risk of colon and rectum cancer over 20 years of follow-up after radiation remained the same across three eras (1973-1980, 1981-1990, and 1991-2000). Radiation-induced second cancers of the colon and rectum may occur 8 years after radiation treatment for cervical cancer.