Sex Differences in Postoperative Outcomes for Men and Women With Colon Cancer in the US Military Health System

Objectives: Biological, behavioral, and health care access differences between men and women may contribute to differences in colon cancer diagnosis and treatment. We compared postoperative outcomes between men and women with colon cancer in the universal access Military Health System (MHS) to better understand sex-based differences in surgery. Methods: We identified patients with stage I to III colon adenocarcinoma receiving surgery in the Military Cancer Epidemiology (MilCanEpi) database between 2001 and 2014. Thirty-day postoperative outcomes included general cardiovascular and respiratory complications; infections (surgical site [SSI], urinary tract [UTI], and systemic); gastrointestinal (GI) complications (hemorrhage, bowel obstruction, ileus, intra-abdominal abscess, and anastomotic leakage); and hospital readmissions. Modified Poisson regression estimated adjusted rate ratios (ARRs) and 95% CIs in association with biological sex for the outcomes. Results: The study included 1073 male (mean age=59.5±13.5 y) and 794 female (mean age=59.6±13.5 y) patients. In the 30-day postoperative period, general complication rates were not different by sex (ARR=1.03, 95% CI: 0.76-1.40 for women vs. men). Female sex was associated with higher rates of UTI (ARR=2.44, 95% CI: 1.63-3.65) and lower rates of GI complications (ARR=0.79, 95% CI: 0.69-0.90) relative to men. There were no sex differences in 30-day hospital readmissions (ARR=0.90, 95% CI: 0.76-1.08 for women vs. men). Conclusions: In the MHS, female sex was associated with higher rates of UTI and lower rates of GI complications relative to men undergoing colon cancer surgery. Factors other than health care access, such as biological differences in pelvic anatomy, physiology, or immune responses, may contribute to observed differences.