Association of sarcopenia with endocrine therapy toxicity in patients with early breast cancer

Endocrine therapy reduces recurrence risk and improves survival in women with hormone receptor-positive breast cancer; however, side effects can decrease quality of life, leading to reduced treatment adherence. Sarcopenia is the loss of skeletal muscle mass that happens with age; it is associated with worse survival and reduced chemotherapy adherence in patients with breast cancer. The impact of sarcopenia on endocrine therapy tolerance has not been investigated. The current study evaluates the associations of sarcopenia with endocrine therapy toxicity and treatment tolerance.

Skeletal muscle mass was measured by bioelectrical impedance spectrometry. Skeletal muscle index (SMI) was calculated to assess for sarcopenia: SMI = (SMM kg)/(patient height, m²). Patients with SMI ≤ 6.75 kg/m² were considered sarcopenic. A chart review was performed to obtain patient characteristics, endocrine therapy toxicity, and early treatment change or termination. Fisher's exact test was performed to associate patient characteristics and outcomes with sarcopenia status.

Four hundred eighty-two patients with stage I-III breast cancer were prescribed endocrine therapy and had undergone sarcopenia evaluation. The median age was 61 years (29-88 years). Sarcopenia was identified in 35% of patients. Twelve percent of patients experienced grade 3-4 endocrine-related toxicities. On multivariable logistic analysis, sarcopenia was associated with increased odds of experiencing endocrine-related side effects (p = 0.006). In addition, patients with sarcopenia stopped or changed their medication due to side effects more often than those without sarcopenia (p = 0.03).

The presence of sarcopenia in patients with EBC represents a potentially modifiable risk factor for more significant endocrine therapy side effects and reduced treatment tolerance.