P254 REAl-world Data from an Italian Compassionate Use Program (CUP) of avelumab first- Line Maintenance (1LM) for locallY advanced or metastatic Urothelial Carcinoma (la/mUC): Outcomes from the READY study in patients (pts) with low tumor burden

Introduction & Objectives: In the JAVELIN Bladder 100 phase 3 trial, avelumab 1LM prolonged Overall Survival (OS) and Progression-Free Survival (PFS) in pts with la/mUC that had not progressed with 1L Platinum-Based Chemotherapy (PBC), supporting its inclusion in updated international treatment guidelines as a recommended option. Before reimbursement was available in Italy, pts with la/mUC could receive avelumab 1LM in a CUP. Pts with low tumor burden have a better prognosis, which may alter benefit-risk considerations for treatment. We report a post hoc subgroup analysis from the CUP in pts with low tumor burden (lymph node [LN]–only disease prior to 1L PBC). Materials & Methods: This prospective, noninterventional CUP enrolled pts from 18 January 2021 to 7 March 2022. Eligible pts had la/mUC that had not progressed with 4-6 cycles of 1L PBC and started avelumab 4-10 weeks after their last dose of PBC. Pts who had disease relapse within 12 mo of prior neoadjuvant or adjuvant systemic therapy were ineligible. Avelumab was provided on physician request and after approval by local ethics committees, per Italian CUP regulations. Results: Of 464 pts enrolled, 138 had LN-only disease prior to 1L PBC and a recorded start date of avelumab treatment. Median age was 69 years; 117 pts (84.8%) were male; ECOG performance status was 0 in 103 (74.6%) and 1 in 35 (25.4%); and Bellmunt prognostic score was 0/1 in 58 (67.4%), 2 in 25 (29.1%), and ≥3 in 3 (3.5%). Prior 1L PBC regimen was cisplatin (cis) + gemcitabine (gem) in 70 pts (50.7%), carboplatin (carbo) + gem in 66 (47.8%), and other in 2 (1.5%). Best response to 1L PBC was complete response in 23 pts (16.7%), partial response in 77 (55.8%), and stable disease in 38 (27.5%). At data cutoff (30 July 2023), median follow-up was 20.3 mo (95% CI, 19.8-20.9). Median OS from the start of avelumab 1LM was not reached (95% CI, not estimable), and the 12-mo OS rate was 79.3% (95% CI, 72.5%-86.1%). In pts who had received 1L cis + gem or 1L carbo + gem, 12-month OS rates were 70.7% (95% CI, 60.0%-81.3%) and 87.7% (95% CI, 79.8%-95.6%), respectively. Median PFS was 12.2 mo (7.7-20.3), and the 12-mo PFS rate was 50.5% (95% CI, 42.2%-58.9%). In 143 treated pts, adverse events of any grade (related or unrelated) occurred in 58 (40.6%); the most common were pruritus (8 [5.6%]), arthralgia (7 [4.9%]), and COVID-19 (6 [4.2%]). Conclusions: Real-world data from Italy show a pronounced clinical benefit with avelumab 1LM treatment in pts with LN-only disease, consistent with prior analyses from JAVELIN Bladder 100. These data provide further support for the use of avelumab 1LM as a standard of care for pts with la/mUC that has not progressed with 1L PBC, including pts with low tumor burden.