Low Muscle Mass in Women May Worsen Breast Cancer Outcomes

Maintaining adequate muscle mass is vital for women undergoing breast cancer treatment. Research indicates that women with higher muscle reserves tend to respond more effectively to therapies such as chemotherapy and radiotherapy. These women also experience fewer complications and have better recovery prospects. Muscle tissue plays a key role in metabolism, influencing inflammatory responses and the absorption of medications, which are critical during cancer treatment.

Conversely, women with low muscle mass face increased risks of toxicity from treatments, leading to a poorer prognosis and lower survival rates. A study conducted at the Ribeirão Preto School of Medicine, part of the University of São Paulo in Brazil, examined women recently diagnosed with breast cancer. Findings revealed that those with diminished muscle mass at the start of follow-up had worse outcomes compared to women with normal muscle levels. The research was published in Discover Oncology.

This investigation was part of a larger analysis focusing on metabolic changes caused by chemotherapy. Researchers assessed muscle mass through CT scans of the lumbar region, and also used bioimpedance analysis to measure phase angle—a quick, non-invasive indicator of body composition. The study involved 54 women with early-stage breast cancer undergoing chemotherapy, all of whom underwent comprehensive assessments prior to treatment.

Nutritionist Mirele Savegnago Mialich Grecco, who led the study, noted that women with breast cancer are prone to muscle loss, decreased muscle quality, and reduced strength during treatment. These changes can predict adverse outcomes, including higher mortality. The study highlighted the importance of assessing body composition, especially in overweight or obese patients where excess weight may obscure muscle deficits.

The study also demonstrated that women with low muscle mass had lower phase angles, which correlated with poorer survival odds. This suggests that phase angle measurement could serve as a practical marker of overall health and prognosis in clinical settings.

In a broader context, breast cancer remains a leading cause of cancer-related death among women worldwide. In Brazil alone, the National Cancer Institute estimates nearly 74,000 new cases annually and approximately 18,000 deaths in recent years. The prevalence of low muscle mass in cancer patients generally ranges from 38% to 70%, with around 40% in breast cancer cases, linking reduced muscle to treatment failure, toxicity, tumor progression, and decreased survival.

Grecco emphasizes that muscle loss during treatment is expected but undesirable. Monitoring body composition can help guide targeted nutritional and physical interventions. Early measures, such as increasing protein intake and promoting resistance and strength exercises, may preserve muscle mass, enhancing resilience to treatment and improving outcomes.