(UroToday.com) The phase 3 JAVELIN Bladder 100 trial, which enrolled patients with advanced urothelial carcinoma that had not progressed with first-line platinum-containing chemotherapy, showed that maintenance therapy with avelumab + best supportive care significantly prolonged overall survival (OS) compared with best supportive care alone (HR 0.69, 95% CI 0.56 to 0.86; 1-sided p = 0.0005).1 However, the optimal timing for starting avelumab after completing first-line chemotherapy is unknown. In the trial, patients received avelumab + best supportive care or best supportive care alone after a treatment-free interval of 4 to 10 weeks from completion of first-line treatment in order to allow resolution of any chemotherapy-related toxicities and tumor assessment to confirm eligibility. At the 2021 American Society of Clinical Oncology (ASCO) 2021 Annual Meeting, Dr. Srikala Sridhar and colleagues presented results of a post hoc analysis assessing efficacy by duration of the treatment-free interval from completion of first-line chemotherapy.