Pectoralis Muscle Wasting During Chemotherapy.

e24069 Background: Chemotherapy is often followed by muscle mass loss which has been associated with frailty. We explored factors associated with change in pectoralis muscle mass after chemotherapy. We hypothesized greater muscle loss with time would be associated with poorer overall survival. Methods: We identified individuals with breast cancer (N = 221), sarcoma (N = 115), and lymphoma (N = 216) who received chemotherapy at the University of Minnesota MHealth Fairview and had CT scans before and after chemotherapy. Right pectoralis muscle area was measured using CORESLICER and indexed to body surface (right pectoralis muscle area [cm2] / body surface [m2]). We calculated quartiles of the indexed pectoralis measure. We restricted our analyses to participants who received a follow-up CT within two years after starting chemotherapy. In a multivariate linear regression, we explored associations of sex, age, BMI, ever-smoking, time since start of chemotherapy, indexed baseline muscle area, stage, type of diagnosis, and cumulative anthracycline dose with relative (%) change in muscle area. In a Cox regression we tested the association of relative muscle change with overall mortality. We used cubic splines to test for nonlinear effects. Results: Of 477 participants (66% female; mean age 61.3 (10.1) years), 366 received anthracyclines, 61 Trastuzumab, and 60 both. The average loss in right pectoral muscle area was -10% for women and -12% for men. We detected nonlinear effects of indexed baseline muscle area, P = 0.03. In a model using quartiles of indexed baseline muscle area, significant predictors of muscle loss included sex (women vs. men, -9.0%, 95% confidence interval (CI) -14.2- -3.7%, P = 0.0008), larger indexed baseline muscle area (quartiles 2, 3, 4 compared with quartile 1, change range -7 - -24%, 95% CI range, -2 - -30%, P-range < 0.0001 – 0.006), smoking (ever vs. never, -4.1%, 95% CI -7.6 - -0.7%, P = 0.02), and diagnosis (sarcoma vs breast cancer, -5.7%, 95% CI -11.1 - -0.3%, P = 0.04). There was no significant association between muscle change and overall survival (median follow-up time 4.1). Conclusions: Being female, larger baseline muscle mass (per m2 body surface), ever-smoking, and a sarcoma diagnosis were associated with greater relative muscle loss after chemotherapy. More data is needed to understand the course of sarcopenia in terms of recovery and survivorship. [Table: see text]