Risk of Colorectal Cancer After Diagnosis of Endometrial Cancer: A Population-Based Study

Purpose Site-specific risk of colorectal cancer (CRC) among survivors of endometrial cancer (EC) is not known. The objective of the present study was to assess the risk of CRC (overall and subsite specific) among EC survivors.Methods A historical cohort study was performed by linking the Manitoba Cancer Registry and the Manitoba Health administrative databases. Each subject diagnosed with EC as her first cancer between 1987 and 2008 was age matched with up to five women with no history of invasive cancer on the index date (date of EC diagnosis). All subjects were followed up to the date of diagnosis of CRC or another cancer, death, migration, or study end point (December 31, 2009). Competing-risk proportional hazards models were used to compare the CRC incidence rates with adjustment for age, history of lower gastrointestinal endoscopy, and socioeconomic status. There were three mutually exclusive (and competing) outcomes: CRC, another primary cancer, and death.Results A total of 3,115 women with EC and 15,084 without EC were followed up for a total of 145,502 person-years. Women diagnosed with EC at age ≤ 50 years had an increased risk of being diagnosed with CRC (all CRC: hazard ratio [HR] = 4.41; 95% CI, 1.47 to 13.26; right-sided CRC: HR = 7.48; 95% CI, 1.29 to 43.28). There was no increased risk of all CRC among women 51 to 65 years of age or those older than 65 years at the time of EC diagnosis. However, women 51 to 65 years of age at EC diagnosis had an increased risk of right-sided CRC (HR = 2.30; 95% CI, 1.05 to 5.01).Conclusion This study suggests young women (age ≤ 50 years) with EC are at increased risk of CRC; risk of right-sided CRC is also increased in women 51 to 65 years old at EC diagnosis.