Hánah N. Rier, Agnes Jager, Stefan Sleijfer, Joost van Rosmalen, Marc C. J. M. Kock, Mark‑David Levin. Breast Cancer Research and Treatment (2018) 168:95–105

Main findings

• Low muscle mass (LMM) and low muscle attenuation (LMA) have been associated with physical disability and mortality of otherwise healthy older adults.
• Muscle attenuation (muscle density) reflects the accumulation of adipose tissue in muscles and is therefore considered a marker of muscle quality.
• Quantitative and qualitative muscle loss are largely age-related, but also occur in the presence of a chronic disease. In cancer patients, body composition parameters, including LMM, LMA and adipose tissue loss have increasingly been related to unfavourable outcomes.
• LMA being a better prognostic marker than LMM.
• In this study Body composition changes during taxane-based therapy were compared with body composition changes during anthracycline-based therapy.
• Body composition measurements were performed before and after completion of first-line palliative chemotherapy and consisted of the measurement of muscle mass and muscle attenuation (MA), which is the density of muscle tissue, with lower muscle density indicating more microscopic fat infiltration of muscle.
• 98 patients. 73 treated with paclitaxel and 25 FAC.
• In patients treated with 4 or more cycles of paclitaxel, MA significantly decreased during treatment (median − 0.9 HU, IQR − 4.2 to + 1.9 HU, p = 0.03), while all other body composition parameters remained stable. No significant changes in body composition were observed in the patients treated with 4 or more cycles of FAC as well.
• Prior chemotherapy on average had a 2.57 HU higher loss of MA compared to patients without prior chemotherapy.
• This study shows that median muscle attenuation significantly decreased during treatment with paclitaxel (− 0.9 HU, p = 0.03). In contrast, in patients treated with anthracycline based chemotherapy, the change of median MA was not statistically significant. The amount of muscle mass and adipose tissue remained stable during treatment in both groups.
• MA is a marker of microscopic fatty infiltration of muscle, and associated with systemic inflammation and poor functional status, similar to cancer cachexia. Therefore, patients with MA decrease during treatment could possibly represent frail patients with higher risk of treatment complications and chemotherapeutic toxicity during successive chemotherapeutic regimens.
• Explanations for the loss of MA during paclitaxel remain speculative, but might be found in several factors, including less physical activity, alterations in muscle composition due to taxane-related myalgia and neuropathy, exposure to (adjuvant) chemotherapy in the past and the impact of routine administration of co-medication, such as corticosteroids.
• As a result, it is not likely that the dexamethasone administration in the patients treated with paclitaxel have caused the decrease of median MA.
• Knowledge regarding changes in body composition during chemotherapy might be important for clinical decision-making because of several reasons. Since increased fat infiltration of muscle represent negative metabolic changes, comparable with the metabolic changes occurring in cancer cachexia, patients with loss of MA might be at increased risk for negative clinical outcomes and might have lower quality of life due to worse physical function.
• It could be hypothesized that patients with decreasing fat mass might experience more chemotherapeutic toxicity from the lipophilic paclitaxel, as a lower volume of distribution to adipose tissue occurs, resulting in higher systemic drug levels.