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Survival Benefit Of Obesity In Stage IV Colorectal Cancer: Better Tolerability Of Chemotherapy?
*Catherine Tran, *Braden Jensen, *Elise Hill, *Austin Stark, *Meghan Mali, *Sarah Bell, *Daniel Berg, Carlos Chan
University of Iowa, Iowa City, IA

OBJECTIVE(S): This study tested the association of obesity and overall survival (OS) in stage IV colorectal cancer (CRC). Obesity is a risk factor for the development of CRC and is considered a negative prognostic factor. Recent studies demonstrate obesity may be associated with improved outcomes in certain diseases.
METHODS: This was a single-institution, retrospective study of patients with stage IV CRC who underwent resection, chemotherapy, or radiation. Patients were grouped by BMI as normal weight (NW), overweight, or obese. Survival probabilities were estimated by Kaplan-Meier and Cox regression models tested factors for association with survival.
RESULTS: This study identified 320 patients, including 108 NW, 109 overweight, and 103 obese patients. The groups did not have significant differences in age, gender, race, primary tumor site, KRAS/BRAF mutational status, T or M stage, or treatment. Obese patients were more likely to be node-positive than NW patients (88 vs. 66%, P = 0.01). At a median follow-up of 65 months, younger age, rectum primary, surgery of the primary tumor or metastases, and chemotherapy were associated with improved overall survival (OS). After adjusting for age at diagnosis, diabetes status, primary site, surgical resection, and chemotherapy, NW and overweight patients had increased risk of death compared to obese patients. The HR for death in NW and overweight patients was 2.0 (95% CI 1.45 - 2.77) and 1.4 (95% HR 1.01 - 1.96), respectively, compared to obese patients. Obese patients underwent longer durations of chemotherapy compared to NW patients (median duration 11.7 vs. 6.5 months, P = 0.01) and had larger changes in BMI vs. NW patients after chemotherapy (median change in BMI -7.7 vs. -3.1%, P = 0.02) without significant differences in severity of chemotherapy side effects.
CONCLUSIONS: In a multivariable analysis, obese patients with stage IV CRC had decreased risk of death and underwent longer duration of chemotherapy compared to NW patients. Obese patients had greater loss in BMI without increased severity of chemotherapy side effects.

Multivariable survival analysis of patients with stage IV colorectal cancer undergoing treatment
CovariateLevelNHR (95% CI)P Value
BMI categoryNormal weight1091.97 (1.41-2.77)<0.001
Overweight1081.41 (1.01-1.96)0.04
Obese103Reference-
Age at diagnosis (per year)3201.01 (1.0 -1.02)0.1
Diabetic (vs. not diabetic)471.61 (1.13-2.3)0.009
Primary SiteColon2081.78 (1.34-2.36)<0.001
Rectum112Reference-
Received surgery (vs. no surgery)2030.3 (0.22-0.4)<0.001
Received chemotherapy (vs. no chemotherapy)2860.23 (0.16-0.35)<0.001


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