Background: Studies have suggested that women with previous diagnoses of gynecologic cancer (cervical, endometrial, or ovarian) have an increased risk for colorectal cancer.
Objective: To quantify risk for colorectal cancer after gynecologic cancer, both overall and for subgroups defined by age at diagnosis, cancer stage at diagnosis, ethnicity, and duration of follow-up.
Design: Retrospective cohort analysis of the Surveillance, Epidemiology, and End Results (SEER) program database from 1974 through1995.
Setting: U.S. cancer registry.
Patients: 21 222 patients with cervical cancer, 51 680 patients with endometrial cancer, and 28 832 patients with ovarian cancer.
Measurements: Standardized incidence ratios (SIRs) were calculated for each gynecologic cancer site and for subgroups to represent the relative risk for colorectal cancer in women with previously diagnosed gynecologic cancer compared with women without gynecologic cancer. Poisson regression methods adjusting simultaneously for all study variables were used to estimate relative risks for colorectal cancer across subgroups with each gynecologic cancer.
Results: Overall, risk for colorectal cancer was elevated among women with previous ovarian cancer (SIR, 1.36 [95% CI, 1.21 to 1.53]). Risk was greatest in women who received a diagnosis before 50 years of age (SIR,3.67 [CI, 2.74 to 4.80]) but was also elevated in women who received a diagnosis between 50 and 64 years of age (SIR, 1.52 [CI, 1.25 to1.83]). The risk for colorectal cancer after endometrial cancer was also elevated substantially if endometrial cancer was diagnosed before the age of 50(SIR, 3.39 [CI, 2.73 to 4.17]). No apparent risk elevation was associated with previous cervical cancer.
Conclusions: Previous endometrial or ovarian cancer, particularly when diagnosed at an early age, increases subsequent risk for colorectal cancer. Greater emphasis on colorectal cancer screening in these populations may be necessary.