What Is Sarcopenia? What Does MUSCLE LOSS Mean in Cancer?

What Is Sarcopenia?

A reduction in muscle mass or its loss is described by the term sarcopenia, which first entered the medical literature in the late 1980s and became a focus of research. Sarcopenia is a public health problem that generally begins in a typical adult's forties and continues thereafter. The problems that accompany it make sarcopenia a serious public health concern.

The development of sarcopenia in older adults increases the risks of functional impairment, disability, falls and fractures, loss of physical independence and death. The cost to the United States health care system of sarcopenia-related disability is thought to exceed $18 billion.

Initially, sarcopenia was seen mainly as an age-related phenomenon. However, increasing research has shown that loss of muscle mass and strength is a more complex and multifaceted issue. A wide variety of factors, including a person's biology, lifestyle and clinical course, influence the development of sarcopenia. Cancer is one of the clinical conditions that cause loss of muscle mass and strength. The effects, prevention and correction of sarcopenia during this disease are subjects of considerable attention.

How Is Sarcopenia Measured?

The method still most frequently used to assess nutritional status is body mass index(BMI). Although BMI is practical, it is insufficient for assessing body composition, meaning the fat/muscle ratio. There are many ways to assess body composition, ranging from simple anthropometric measurements to MR imaging . On computed tomography (CT), evaluating a muscle slice at the level of the 3rd lumbar vertebra (L3) is a valuable and readily applicable method that can provide information about muscle quantity and structural composition (the muscle tissue/fat tissue ratio in the cross-section). CT is readily applicable because it is already frequently used in cancer diagnosis and follow-up, which also enables extensive research in this area.

Why Is Sarcopenia Important in Cancer?

In patients with cancer, the reported prevalence of sarcopenia ranges from 11 - 74% . Patients who have both cancer and sarcopenia frequently exhibit many unfavorable indicators of disease course. In other words, muscle mass loss in cancer patients is associated with a poor prognosis (an unfavorable course). Numerous studies have evaluated sarcopenia and its effects on outcomes in patients with cancer. In a recent meta-analysis , data from 7843 patients with cancershowed lower overall survival in patients with low muscle mass.

Many studies show an inverse relationship between muscle mass and chemotherapy toxicity (side effects). As is known, the doses of certain chemotherapy drugs are adjusted not by weight but by body surface area (BSA). The increase in side effects associated with sarcopenia is more pronounced with these chemotherapy drugs. A recently published study evaluating outcomes in 533 patientsshowed that, among patients receiving the FOLFOX regimen for early-stage colon cancer, those with low muscle mass more frequently experienced early chemotherapy interruptions and treatment delays. Another study with similar results found greater chemotherapy toxicity in women with low muscle mass. Among orally administered cancer drugs, sorafenib (Nexavar) was investigated in a study that showed side effects requiring dose reductions were more common in patients with sarcopenia. Sarcopenia also adversely affects the surgical process and outcomes. Patients with sarcopenia experience delayed surgical wound healing, increased postoperative infection rates and longer hospital stays.

Sarcopenia Should Be Routinely Assessed in Patients With Cancer

It is very important first to identify sarcopenia through appropriate analyses, given its impact on the disease course. Routine assessments based on CT imaging should therefore be performed during follow-up. Semiautomated software that uses CT data is available, but it has not yet become part of routine radiology practice.

Treatment of Sarcopenia in Cancer

Oncology patients have several prominent approaches being discussed and investigated for managing sarcopenia:

• nutritional support,
• medication support and
• exercise

.

Studies evaluating nutritional supplements such as vitamins, protein and essential amino acids have not provided sufficient evidence of benefit. Research has examined molecules such as testosterone acting through androgen receptors, interleukin 1 alpha and myostatin, but none has yet been approved for this use. Studies with anamorelin, a receptor agonist of ghrelin, which acts particularly through the appetite mechanism, have been promising. However, it has not been approved because it does not increase muscle strength or affect survival compared with the control group.

Exercise has shown beneficial effects in a meta-analysis including 1199 patients with prostate cancer . According to this study, patients enrolled in a resistance exercise program had a significant increase in muscle mass.

Summary and Conclusion

Although numerous studies to date show an association between sarcopenia and unfavorable outcomes, the vast majority are retrospective (looking backward). Factors linked to muscle mass loss other than age have been identified, but the underlying mechanisms are not yet fully understood. In short, prospective (forward-looking) research is needed to clarify this area.

In oncology, the doses of many chemotherapy drugs are determined by patients' body surface area. BSA is calculated from height and weight. Two patients with the same BSA may have different muscle/fat ratios. Therefore, even with the same BSA, differences in body composition are more decisive in drug side effects that vary between patients. Research is also needed to clarify this aspect.

In conclusion, although the adverse effects of reduced muscle mass in cancer patients are not in dispute, understanding the mechanisms and identifying approaches to reverse sarcopenia remain important topics for discussion and research. Assessing sarcopenia in patients with cancer should be considered a routine part of oncology care.