Maintaining muscle mass has been shown to be a key factor in how well patients respond to cancer treatment. People with higher muscle mass typically respond better to chemotherapy and radiotherapy, experience fewer complications, and recover more effectively.
This is because muscle supports healthy metabolism, helps manage inflammation, and improves how the body absorbs cancer-fighting drugs. In contrast, patients with low muscle mass face a greater risk of severe side effects, poorer outcomes, and lower chances of survival.
A recent study from the Ribeirão Preto School of Medicine at the University of São Paulo (FMRP-USP), Brazil, reinforces these concerns. The study focused on women newly diagnosed with early-stage breast cancer and found that those with lower muscle mass at the beginning of treatment had a significantly worse prognosis.
Funded by FAPESP and published in Discover Oncology, the study aimed to identify easy and affordable ways to measure and track muscle health in clinical settings.
The researchers examined data from 54 patients treated at a major teaching hospital in Brazil. All had recently been diagnosed with early breast cancer and were referred for chemotherapy.
Before beginning treatment, the women underwent several tests to assess their physical condition. These included body scans (CT), bioimpedance testing (a non-invasive way to measure body composition), handgrip strength, walking speed, and blood tests.
Mirele Savegnago Mialich Grecco, a nutritionist and one of the study’s authors, explained that breast cancer patients often experience muscle loss, decreased muscle quality, and weakness during treatment. These changes are closely tied to worse outcomes—including shorter survival.
One challenge, Grecco noted, is that many breast cancer patients are overweight or obese. This can give a misleading impression of health, masking the fact that they may still have low muscle mass. “Excess body weight can hide poor muscle condition. If we don’t take a closer look, we may miss it altogether,” she said.
CT scans are typically done as part of routine care for breast cancer patients, but they can also be used to evaluate muscle mass. In this study, the researchers analyzed images from the L3 vertebra (a bone in the lower back) to get an accurate view of each woman’s muscle mass before treatment.
However, because CT scans are not always practical or affordable in all settings, the researchers also tested a more accessible tool: phase angle, or PhA. This number is calculated using bioimpedance analysis and reflects the health of cells and membranes. Lower PhA values indicate poorer overall health and were found in women with low muscle mass.
Five years after the initial measurements, the researchers reviewed the patients’ medical records to assess outcomes. They found that women with low muscle mass before treatment had significantly lower survival rates—even though their cancers had not spread (non-metastatic).
Those same women also had lower phase angles, further linking poor muscle health to lower survival, regardless of age or cancer stage.
Grecco said these findings support using phase angle as a simple, low-cost method to monitor muscle health and predict outcomes in breast cancer patients. It can help doctors and dietitians identify at-risk patients early and intervene with tailored nutrition and exercise strategies.
Breast cancer is one of the leading causes of cancer death among women. In Brazil, nearly 74,000 new cases and 18,000 deaths are expected annually between 2023 and 2025.
In 2023 alone, over 60,000 cases were recorded, including many in women under 40. With around 40% of breast cancer patients showing signs of low muscle mass, the need for early and accurate assessment is critical.
Grecco emphasized that muscle loss during treatment is common but not unavoidable. The goal is not necessarily to build more muscle, but to preserve as much as possible. She recommends that healthcare providers begin monitoring muscle mass as soon as a patient is diagnosed.
From there, they can provide tailored protein intake guidelines and encourage participation in resistance or strength-building exercise programs as appropriate.
“We want to intervene early,” Grecco said. “If we give women the right amount of protein and help them stay physically active, we can protect their muscle mass and improve how well they respond to treatment.”
The study’s message is clear: muscle matters. And simple tools like bioimpedance and phase angle analysis could help bring personalized care to more breast cancer patients—ensuring they get the support they need to not just survive, but recover well.
If you care about breast cancer, please read studies about how eating patterns help ward off breast cancer, and soy and plant compounds may prevent breast cancer recurrence.
For more health information, please see recent studies about how your grocery list can help guard against caner, and a simple way to fight aging and cancer.
The research findings can be found in Discover Oncology.
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