Several recent publications have shown that a reduced fat free mass is associated with a reduced survival and increased treatment toxicity in oncologic patients. However, most of these data are retrospective and evaluate heterogeneous patient populations. The aim of this study is to evaluate the predictive value of body composition on treatment toxicity and prognosis in a homogeneous population of metastatic colorectal cancer patients treated with at least two prior lines of chemotherapy, a population that has not been studied to date.

Body composition (skeletal muscle, visceral fat, subcutaneous fat surface and attenuation in Hounsfield units) was assessed retrospectively by CT scanner at the level of L3 in 88 patients treated in a phase 2 clinical trials using the Dosisoft software. Toxicity, progression free survival and overall survival were assessed prospectively as were anthropometric data (height and weight).

Mean body mass index was 25.4 and 52% of the patients were either overweight or obese. Sarcopenia was present in 80% of the whole patient population, and in 50% of obese patients. Median overall survival was decreased in patients whose muscle index was below the median (12.0 vs. 7.8 months). By contrast, the usual diagnostic criteria for sarcopenia were not associated with a statistically significant difference in survival. We also found that the mean attenuation of visceral and subcutaneous fat were correlated with median overall survival, with a lower attenuation being associated with a better survival (10.8 vs. 6.7 months for visceral fat, 10.3 vs. 7.5 months for subcutaneous fat). A low visceral fat mean attenuation was also associated with a better progression free survival (5.1 vs. 3.6 months). Finally, none of the body composition parameters evaluated in this study was associated with treatment toxicity.

A reduced muscle mass is associated with a bad prognosis in metastatic colorectal cancer patients, but the usual diagnostic criteria of sarcopenia do not predict survival in our patient population. A reduced adipose tissue attenuation is correlated with a better prognosis. By contrast with other publications, body composition did not predict treatment toxicity in our study.