Measuring Muscle Composition Predicts Chemotherapy Toxicity

Early-stage breast cancer patients with low muscle quality and quantity have twice the risk of hospitalization.

An individual’s body composition can predict whether they face a high-risk of adverse events (AEs) from chemotherapy for early-stage breast cancer.

In a study published in Clinical Cancer Research, investigators found that low measures of muscle quality and quantity in individuals with early-stage breast cancer are associated with serious AEs and hospitalizations.

The findings could help clinicians more accurately determine chemotherapy dosing, thereby lowering the risk of AEs, according to investigators.

“The formula currently used in clinical practice for chemotherapy dosing—–body surface area––doesn’t really help us predict which patients will develop treatment-related toxicity,” said first author Shlomit Strulov Shachar, MD. “This study supports the concept that body composition may be more sensitive than the formula that has been used for decades to dose chemotherapy.”

Although prior research shows a link between age-related muscle loss and poor overall survival in patients with solid tumors, little was known about the risks of patients with early-stage breast cancer developing treatment-related AEs based on muscle composition.

“More and more studies are showing that muscle mass, especially loss of muscle and function, or so-called sarcopenia, is associated with poor outcomes, poor survival, and more toxicity with cancer treatment,” said co-author Hyman B. Muss, MD. “It may be that muscle mass is related to the metabolism of chemotherapy in your body, as well as your general fitness. So people with a low muscle mass may simply be less fit, and their bodies don’t tolerate chemotherapy treatments as well. These patients may be especially vulnerable to treatment effects.”

For the study, investigators reviewed medical data from 151 patients treated for early breast cancer at the NC Cancer Hospital between 2008 and 2013, of whom approximately one-third experienced serious chemotherapy-induced AEs.

Each of the patients’ existing abdominal CT scans were analyzed to produce an estimate of fat and muscle composition. Both muscle quality and quantity—–including the indirect fat content—was measured to develop a “skeletal muscle gauge.”

The investigators examined the participants’ medical records to determine who experienced serious chemotherapy AEs, including hospitalization, gastrointestinal complications including nausea or vomiting, depletion of important blood cells, and neuropathy in the arms or legs.

The results of the study showed that patients with low muscle quality and quantity had a higher risk of blood-related toxicities, gastrointestinal AEs, and neuropathy. Furthermore, the same patients had twice the risk of hospitalization after being adjusted for age and body surface area.

Compared with other body composition measures, such as body mass index, the investigators found that skeletal muscle gauge was the most predictive of toxicity.

Measuring muscle composition could be helpful in predicting which patients will experience AEs from chemotherapy and in determining appropriate drug doses, according to the authors.

“Hospitalization is a terrible thing for patients, especially for older patients after chemotherapy,” Muss said. “We need better ways of predicting who might be hospitalized for treatment [AEs]. “If we can give a little less dose initially, we might be able to lower toxicities without sacrificing effectiveness. By improving the therapeutic index, we can retain the benefits while minimizing the risks of treatment.”

Dr Shachar noted that improving chemotherapy dosing is crucial in the clinical landscape.

“For me, as a physician in the clinic, it’s very troubling when patients get toxicity from therapy,” Shachar said. “We need to deliver the best therapies we can with less toxicity. We need to think carefully about how to dose patients other than relying on just height and weight.”