PURPOSE The purpose of this study was to elucidate the effect of decreased muscle mass on the toxicity and survival of patients with colon cancer treated with adjuvant chemotherapy after surgery.

METHODS We reviewed the data of 229 consecutive patients with stage III colon cancer who received adjuvant oxaliplatin, 5-fluorouracil, and leucovorin chemotherapy at a single center between 2003 and 2010. Baseline muscle mass was assessed by measuring the cross-sectional area of the psoas muscle at the level of the fourth lumbar vertebra on computed tomography images. Effects of muscle mass on toxicity of chemotherapy and survival were assessed.

RESULTS The median age of the 229 patients was 61 years (range, 28-80) and 134 (58.5 %) were men. The mean psoas muscle mass index (PI, psoas muscle area divided by height(2) [mm(2)/m(2)]) was 548.3. A 1 SD decrement in the PI was associated with an increase in all grade 3-4 toxicities in univariate (OR = 1.69, 95 % CI = 1.18-2.27) and multivariate (OR = 1.56, 95 % CI = 1.05-2.38) analyses. In univariate analysis, the PI was not associated with overall survival. However, multivariate analysis showed that a 1 SD decrement in the PI increased the hazard of overall mortality by 85 % (HR = 1.85, 95 % CI = 1.10-3.13). This effect of the PI on mortality was maintained in subgroup analyses, especially in older and obese patients.

CONCLUSIONS Decreased muscle mass was associated with increased risk of grade 3-4 toxicity and poor prognosis in patients with stage III colon cancer.