Obesity, survival, and chemotherapy outcomes in stage IV colorectal cancer: a retrospective study

Obesity increases risk for colorectal cancer (CRC) development and historically has been connected to poor outcomes. The obesity paradox describes recent data showing that obesity may be protective in some diseases. This study examined the association between obesity and overall survival (OS) in stage IV CRC, evaluating factors that may contribute to disease course. This was a single-institution, retrospective study of patients with stage IV CRC who underwent resection, chemotherapy, and/or radiation. Patients were grouped by body mass index (BMI) at diagnosis, as normal weight (NW), overweight, or obese. Cox regression models were used to estimate the effects of patient, disease, and treatment characteristics on OS. 320 patients with stage IV CRC were identified, including 108 NW, 109 overweight, and 103 obese patients. No statistically significant differences were found in age, sex, race, primary tumor site, KRAS/BRAF mutational status, tumor stage, or treatment modality between groups. Obese patients more frequently had higher node-positive disease. Duration of chemotherapy significantly differed by BMI (median duration: NW = 6.5 months, overweight = 6.2, and obese = 11.7, p = 0.04). Chemotherapy adverse event scores and reasons for chemotherapy cessation did not differ by BMI group. On multivariable analysis, NW and overweight patients were at increased risk of death compared to obese patients (NW: HR 1.95, 95% CI 1.39–2.73; overweight: HR 1.43, 95% CI 1.03–1.99). Obesity at diagnosis is associated with improved OS in stage IV CRC. Patients with obesity underwent a longer duration of chemotherapy and experienced greater decreases in BMI during this period.