We showed in a previous study that the PG-SGA score is associated with survival and chemotherapy-related toxicities in metastatic colorectal cancer (mCRC) patients. The objective was to evaluate the association between pretherapeutic sarcopenia and variation in skeletal muscle index (SMI) during treatment with these outcomes in the same population.

This prospective, multicenter, observational study enrolled non-pretreated mCRC patients. SMI was measured on routine CT scan at day 0 (D0) and day 60 (D60). Nutritional factors were collected at D0. Progression-free survival (PFS) and overall survival (OS) were calculated from treatment start.

149 patients were included from 7/2013 to 11/2016. Pretherapeutic sarcopenia was not significantly associated with survival or chemotherapy-related toxicities. The decrease in SMI > 14% was significantly associated with shorter PFS (6 vs 9 mo; HR 1.8, 95% CI 1.1−3.1, p = 0.02) and OS (8.5 vs 26 mo; HR 2.6, 95% CI 1.4−4.8, p = 0.002), independently of hypoalbuminemia and malnutrition defined by PG-SGA. Patients with a SMI decrease > 14% had a higher rate of grade ≥ 2 clinical toxicities (40% vs 22%, OR 3.0, 95% CI 1.2−7.7, p = 0.02), but the difference was not statistically significant in multivariable analysis.

To our knowledge, this is the first study to assess prospectively the association of skeletal muscle loss with survival and treatment toxicities in non-pretreated patients with mCRC. Pretherapeutic sarcopenia was not associated with poor outcomes, but the loss of skeletal muscle mass within 60 days from treatment start was highly prognostic, independently of other prognostic and nutritional factors.