Objectives: Evidence is accumulating supporting the use of screening for colorectal cancer. Patients at higher risk for colorectal cancer are more likely to benefit from screening. Women with breast, endometrial, or ovarian cancer are often classified as at high risk for subsequent colorectal cancer, and are urged to undergo screening, but the basis for this is uncertain.
Methods: We performed a meta-analysis of published data to assess the risk of colorectal cancer after these cancers.
Results: Based on 154,270 women and 779,251 person-yr of observation (PYO) after breast cancer, 37,266 women and 229,498 PYO after endometrial cancer, and 41,366 women and 126,688 PYO after ovarian cancer, the age-adjusted relative risk (95% CI) for colorectal cancer after breast cancer was 1.1 (1.07, 1.19), after endometrial cancer 1.4 (1.32, 1.55), and after ovarian cancer 1.6 (1.40, 1.80).
Conclusions: 1) Women with a history of breast, endometrial, or ovarian cancer are at a statistically significant increased risk for subsequent colorectal cancer. 2) Women with a history of endometrial or ovarian cancer are at higher risk than are women with breast cancer, but ascertainment bias from heightened medical surveillance after the diagnosis of a gynecologic malignancy may contribute to this observed increase in risk. 3) The association between these cancers and colorectal cancer suggests common etiologic factors, either environmental or genetic, but the degree of increased risk is small.