Low skeletal muscle radiodensity predicts response to avelumab maintenance treatment in patients with metastatic urothelial carcinoma

Background: The JAVELIN Bladder 100 trial demonstrated a significant survival benefit of avelumab maintenance therapy over best supportive care in patients with locally advanced or metastatic urothelial carcinoma (la/mUC) who achieved disease control after platinum-based chemotherapy. Although avelumab maintenance therapy is generally well tolerated, some patients experience rapid progression and prognostic factors are not well established. Methods: In this retrospective study, we investigated the prognostic significance of computed tomography–derived body composition indicators in 57 patients with la/mUC who received avelumab maintenance therapy between January 2019 and November 2023. These patients were from within a cohort of 85 patients who underwent first-line platinum-based chemotherapy. Patients were divided into two groups based on a low or high skeletal muscle radiodensity (SMD). Prognostic factors were determined by univariate and multivariate analyses. Results: Among patients treated with avelumab, median progression-free survival (PFS) was 6.4 months in the high SMD group versus 4.8 months in the low SMD group, while median overall survival was not reached versus 16.7 months, respectively. In a Cox proportional hazards model, only high SMD indicated a favorable prognosis for PFS (hazard ratio [HR]: 2.31, 95% confidence interval [CI]: 1.25–4.28), while high SMD was the independent predictor for better overall survival (HR: 2.29, 95% CI: 1.04–5.05). Discussion: Such results suggest that SMD is a potential prognostic factor for la/mUC cases undergoing avelumab maintenance therapy.