Skeletal Muscle Mass in Women With Breast Cancer: Evaluation of Agreement Between Different Methods.

Background: The loss of muscle mass, which is the main component of sarcopenia, is a common condition in women with breast cancer. Thus, novel, simple, accessible methods capable of diagnosing this condition in clinical practice have been investigated. Objective: To assess the diagnostic accuracy of an anthropometric equation in predicting the skeletal muscle mass index in women with breast cancer. Methods: An observational cross-sectional study with women ≥ 20 years of age with up to 12 months since the diagnosis of breast cancer having been submitted to dual-energy X-ray absorptiometry (DXA) for the determination of skeletal muscle mass (SMM). Sociodemographic, clinical, and behavioral data were collected. Body mass (kg), height (m), and calf circumference (CC) (cm) were measured. SMM was also obtained through an anthropometric equation. Agreement analysis was performed. Receiver operating characteristic curve analysis, sensitivity, and specificity were calculated. Results: A total of 135 women were analyzed (55 ± 11.3 years). The sample was predominantly nonwhite (69.7%), with ≤ 6 months since diagnosis (81.5%), insufficiently active (59.3%), and with invasive breast carcinoma (70.4%). The Bland-Altman test showed satisfactory agreement between SMM obtained by the anthropometric equation and the reference method (DXA) for adults and older women. For adults, Cronbach's alpha was 0.79, the ICC was 0.79, and the mean error was 0.007 kg/m Conclusion: Satisfactory agreement was found between SMM obtained by the anthropometric equation and the reference method in both adults and older women. This equation proved to be an effective, simple, and safe tool for the identification of SMM and, consequently, for the screening of sarcopenia in women with breast cancer in clinical practice.