Impact of Low Muscle Mass on Breast Cancer Prognosis

Recent research indicates that women diagnosed with breast cancer and exhibiting low muscle mass may face a poorer prognosis during treatment. It has been established that maintaining muscle mass is critical for patients undergoing cancer therapies, as individuals with higher muscle levels generally respond more favorably to treatments such as chemotherapy and radiotherapy. Additionally, they encounter fewer complications and experience more effective recovery processes.

Muscle tissue plays a vital role in metabolism, aiding in the regulation of inflammatory responses and drug absorption. In contrast, cancer patients with diminished muscle mass are at an increased risk of treatment-related toxicity, which can lead to unfavorable outcomes and a decrease in survival rates.

A study conducted at the Ribeirão Preto School of Medicine, University of São Paulo (FMRP-USP), Brazil, investigated the correlation between muscle mass and breast cancer prognosis. The findings revealed that women with lower muscle mass at the commencement of treatment exhibited a significantly worse prognosis compared to their counterparts with normal muscle mass. These results were published in the journal Discover Oncology.

This research forms part of a broader analysis examining metabolic changes associated with chemotherapy in breast cancer patients. The objective was to explore the relationships between muscle mass indicators assessed via computed tomography and phase angle measurements obtained through bioimpedance analysis.

A total of 54 women, all recently diagnosed with early-stage breast cancer and referred for chemotherapy, participated in the study. Prior to initiating treatment, each patient underwent comprehensive assessments, including anthropometric evaluations, bioimpedance testing, CT scans focusing on the third lumbar vertebra, and physical function tests such as handgrip strength and gait speed evaluations. Blood tests were also conducted.

According to the lead nutritionist involved in the study, women with breast cancer often experience significant muscle mass loss, decreased muscle quality, and reduced strength during treatment. These changes are indicative of adverse outcomes, including increased mortality risks.

The study's focus on this specific demographic is important, as many breast cancer patients may be overweight or obese, which can obscure their actual body composition status. The presence of excess weight can misleadingly suggest a healthier muscle reserve than exists.

Data from CT scans, routinely performed for these patients, were utilized for muscle mass analysis. Images of the lumbar region were examined to determine the quantity and quality of muscle mass in women prior to chemotherapy. In addition, the researchers assessed phase angle as an alternative evaluation method, which is associated with membrane integrity and derived from bioimpedance analysis. This approach is quick, non-invasive, and can effectively reflect body composition.

Five years later, patient medical records were reviewed to assess mortality rates. The findings indicated that women with non-metastatic breast cancer and low muscle mass had a considerably lower survival rate compared to those with normal muscle mass. Furthermore, lower phase angles were also noted among individuals with reduced muscle mass, correlating with poorer prognoses and negatively impacting survival rates, irrespective of age or cancer stage. This suggests that phase angle measurement could serve as a valuable clinical tool for assessing patient prognosis.

Breast cancer remains one of the leading causes of cancer mortality among women. In Brazil, the National Cancer Institute (INCA) estimates that nearly 74,000 new cases occur annually, resulting in approximately 18,000 deaths between 2023 and 2025. In 2023 alone, the public health system reported 60,866 cases of breast cancer in women, with 11% of these patients under the age of 40.

The prevalence of low muscle mass among cancer patients is reported to vary between 38% to 70%. Specifically for breast cancer patients, studies suggest a prevalence near 40%. Reduced muscle mass has been linked to treatment failure, chemotherapy toxicity, decreased physical activity, tumor progression, and shorter survival rates.

As muscle mass loss during cancer treatment is common yet undesirable, accurately monitoring body composition is essential. This enables healthcare providers to implement targeted nutritional interventions, particularly in populations where increased adiposity may mask underlying changes in muscle mass.

The study aims to identify practical measures to be integrated into clinical routines, allowing healthcare professionals to intervene more promptly. Suggestions include an early assessment of protein intake for newly diagnosed patients and referrals to physical exercise programs that emphasize resistance and strength training to help mitigate muscle loss during treatment.