Muscles May Provide Insight to Chemotherapy Side Effects

Muscle composition may be predictive of chemotherapy toxicity.

A new study published by Clinical Cancer Research suggests that a patient’s muscles may hold clues to predicting chemotherapy side effects that could lead to hospitalization.

While chemotherapy has long been the standard treatment for various cancers, it can also elicit serious, sometimes life-threatening side effects. Physicians are not only tasked with treating patients, but predicting who will experience side effects that can be difficult to manage.

In the study, the authors found that low muscle mass and poor muscle quality could be used to predict serious side effects of chemotherapy and hospitalization. Based on these findings, the authors suggest that measuring muscle composition could be helpful in clinical practice, and in determining doses.

“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 study author 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.”

Previous research has linked age-related muscle loss to poor survival in patients with solid tumors, but less is known about early-stage breast cancer and 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 study 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.”

Included in the study were 151 patients treated for early-stage breast cancer between 2008 and 2013. Of these patients, one-third experienced serious chemotherapy-related side effects.

The authors examined abdominal CT scans for each patient to estimate fat and muscle composition. They created a skeletal muscle gauge for each patient by measuring muscle quality and quantity, according to the study.

Patient medical records were then analyzed to discover who experienced chemotherapy-related side effects, such as hospitalization, gastrointestinal issues, nausea, vomiting, blood cell depletion, and neuropathy.

The study authors found that patients with poor muscle composition had a higher risk of blood-related toxicities, gastrointestinal problems, and neuropathy. These patients also were observed to have twice the risk of hospitalization, even when age and body surface area was adjusted for.

Despite other body measures, skeletal muscle gauge was observed to be the most accurate predictor of chemotherapy toxicity, according to the study.

“Hospitalization is a terrible thing for patients, especially for older patients after chemotherapy,” Dr Muss said. “We need better ways of predicting who might be hospitalized for treatment side effects. 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.”

The authors said that improving chemotherapy dosing is significant, and has the potential to improve patient outcomes.

“For me, as a physician in the clinic, it’s very troubling when patients get toxicity from therapy,” Dr Shachar concluded. “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.”