Strength-to-muscle radiodensity: A potential new index for muscle quality

Although it is widely recognized that muscle quality significantly influences adverse outcomes in patients with cancer, the precise definition of muscle quality remains elusive. The muscle quality index (MQI), also known as muscle-specific strength, is a relatively recent functional concept of muscle quality. It is obtained through the ratio of muscle strength to muscle mass, but its predictive value in patients with cancer remains unknown. In this study, we explored the prognostic significance of MQI in patients with cancer. Furthermore, we introduce and assess the prognostic potential of a novel muscle quality metric: the strength-to-muscle-radiodensity index (SMRi). A secondary analysis was conducted on a prospective cohort study. CT scans were opportunistically used to assess body composition parameters, including skeletal muscle mass (SM in cm2) and muscle radiodensity (SMD in HU) at the third lumbar vertebra (L3). Handgrip strength (HGS) was measured. MQICT was calculated using the ratio of HGS to SM (cm2). SMRi was calculated as the ratio of HGS to SMD (HU). For analysis purposes, low MQICT and SMRi were defined using two approaches: statistical cutoffs associated with survival, and median-based distribution data. A total of 250 patients were included (52.8% females, 52% adults, 20–90 years). Gastrointestinal tumors and stage III-IV were the most frequent diagnosis and stages. SMRi and MQICT were strongly positively correlated (ρ = 0.71 P