Associations Between Psoas Muscle Area (Pma) And Density (Pmd) With Phase I Oncology Clinical Trial Outcomes.

7007 Background: Malnutrition and cancer cachexia can lead to loss of muscle mass (sarcopenia) and are associated with poor outcomes. Muscle status can be evaluated by computed tomography (CT)-based radiographic measures, specifically at the L3 vertebrae where the psoas and other core muscles reside. We previously found that baseline malnutrition was associated with worse phase 1 clinical trial outcomes including increased toxicity and reduced survival (Jain et al. Oncologist, 2019). We sought to evaluate the relationship between muscle status and phase 1 trial outcomes. Methods: CT-based psoas muscle area (PMA) and psoas muscle density (PMD) were evaluated in 83 patients who enrolled in a phase 1 trial. We localized the L3 vertebral body on axial imaging and manually outlined the psoas muscle to calculate PMA (standardized to height) and PMD. Two reviewers independently conducted the analyses. We stratified patients by having a PMA or PMD above or below the group’s median. We evaluated for associations between PMA/PMD and the following clinical trial outcomes: rates of grade ≥ 3 toxicity, frequency of dose reductions/interruptions, hospitalizations, tumor response, duration on study (DOS), and overall survival (OS). We also evaluated for correlations between PMA/PMD and a validated measure of nutritional status, the PG-SGA. Chi-square analysis was used to determine statistical significance between groups. Kaplan-Meier curves were used to compare DOS and OS. Results: 83 patients were included (38 male, 45 female), with a median age of 60 (range 28-85). The most common cancer type was gastrointestinal (33%). Mean PMA was 2.89 cm2/m2 (range 1.41-5.72) and mean PMD 37.77 Hounsfield units (range 13.27-56.18). PMA above the median was associated with a reduced risk of grade ≥ 3 toxicity (32.5% vs 67.4%, p = 0.001). There was no association between PMD and grade ≥ 3 toxicity, or between PMA/PMD and other phase 1 trial outcomes. There was a significant correlation between nutritional status and PMA (r = -0.278, p = 0.01) but not PMD. Conclusions: PMA and PMD are readily available CT-based measures of muscle status. In oncology phase 1 clinical trial participants, lower baseline PMA was associated with a two-fold increased risk of grade ≥ 3 toxicity. Baseline PMA was moderately correlated with nutritional status which was previously shown to be associated with poor trial outcomes. More research is necessary to further understand the specific mechanisms by which nutritional status and muscle mass may influence toxicity risk in this population.