A recent study at Yonsei Cancer Center has identified low skeletal muscle radiodensity (SMD) as a significant predictor of poor treatment outcomes in patients with hormone receptor-positive, HER2-negative advanced breast cancer. 

Published on Dec. 17 in the Journal of Cachexia, Sarcopenia and Muscle, the research analyzed body composition data from CT scans of 247 women who received a combination of CDK 4/6 inhibitors and aromatase inhibitors as first-line therapy at Yonsei Cancer Center.

The study found that patients with low SMD had a higher risk of disease progression and shorter progression-free survival compared to those with normal muscle density. 

Led by Professors Kim Hyun-wook and Kim Min-hwan from Yonsei Cancer Center’s Division of Medical Oncology, along with Professor Hong Nam-ki and researcher Han Soo-kyeong from Severance Hospital’s Endocrine Research Institute, the team explored the impact of muscle fat infiltration, known as myosteatosis, on treatment response. While myosteatosis has been linked to increased risk of cardiovascular events and mortality, its effect on breast cancer treatment was previously unclear.

The researchers found that myosteatosis, assessed through CT body composition analysis at the third lumbar spine (L3), significantly reduced treatment effectiveness.

This was particularly true in premenopausal women and those without metastasis to the lungs or liver. Patients with low muscle radiodensity had an 84 percent higher risk of disease progression compared to those with normal radiodensity. The study also revealed that premenopausal women with myosteatosis were more likely to experience treatment resistance, potentially due to underlying metabolic dysfunction.

Professor Kim emphasized that SMD could serve as an important predictor of treatment efficacy and called for the integration of nutrition management and exercise therapy to improve muscle quality in breast cancer patients.