Skeletal muscle loss during anti-EGFR combined chemotherapy regimens predicts poor prognosis in patients with RAS wild metastatic colorectal cancer

Purpose We aimed to assess whether anti-EGFR combined chemotherapy regimens are related with loss of skeletal muscle mass and to compare cetuximab and panitumumab therapies in the aspect of skeletal muscle area change as well as to assess whether skeletal muscle mass loss has prognostic significance in the RAS wild mCRC patients. Materials and methods A total of 56 patients (30 patients in cetuximab arm and 26 patients in panitumumab) who had computed tomography images were retrospectively evaluated at the diagnosis and follow up during the treatment period before progression. Results During treatment period 24 patients (42.8%) had muscle loss. Of these, 7 (29.2%) patients were treated at first-line and 17 (70.8%) patients were treated at second-line setting. There was no significant difference in the aspect of skeletal muscle loss among cetuximab and panitumumab combined treatment regimens. Median PFS was 9.1 (8.6–9.6) months in muscle loss group and 13.9 (7.2–20.6) months in muscle stable group ( p = 0.001). Median OS was 23.4 (95% CI 15.8–31.0) months in muscle stable group and 19.1 (95% CI 17.0–21.3) months in muscle loss group ( p = 0.57) at first-line setting. For second-line, median OS was 21.2 (14.7–27.7) months in muscle stable group and 14.4 (6.0-22.4) months in muscle loss group ( p = 0.003). Conclusions Decrease in skeletal muscle mass before progression on CT imaging is an independent indicator for shorter PFS value in RAS WT mCRC patients who received anti-EGFR combined chemotherapy regimens at both the first and second-line settings. Beside that shorter overall survival values also were significantly seen in patients who had muscle loss during anti-EGFR therapy in the second-line setting.