Myosteatosis is prognostic in metastatic melanoma treated with nivolumab.

Background: While immunotherapy agents have improved outcomes in metastatic melanoma (MM), predictive biomarkers in these patients are lacking. Parameters identified from body composition analysis, such as low SMD (also termed myosteatosis), may prognosticate MM patients on immunotherapy.

Methods: In this retrospective study, 44 MM patients received nivolumab, either as monotherapy or in combination with ipilimumab. Pre-treatment computed tomography (CT) scans were analyzed to determine skeletal muscle density (SMD) in Hounsfield units (HU) and muscle surface area (MSA) in cm at L3. MSA was used to determine nivolumab dosing in mg/cm.

Results: Low SMD was associated with worse overall survival (OS) by log rank test (median 12.03 vs. 34.96 months, p = 0.001) and in multivariate analysis when accounting for age, sex, performance status, and number of prior lines of therapy (HR 4.40, 95% CI 1.44-13.42, p = 0.009). Lower nivolumab dosing by MSA was significantly associated with improved OS (median 42.9 vs. 12.3 months, p < 0.001). This association remained significant in multivariate analysis with age, sex, performance status, and number of prior lines of therapy (HR 0.05, 95% CI 0.01-0.30, p = 0.001). Neither SMD nor higher nivolumab dose per MSA were associated with increased incidence of treatment toxicity.

Conclusions: Low SMD is prognostic in MM treated with nivolumab immunotherapy. Presence of myosteatosis or higher nivolumab dose based on body composition did not predict treatment toxicity.