Real-world (rw) treatment (tx) patterns and clinical outcomes among patients (pts) with metastatic urothelial carcinoma (mUC) receiving first-line (1L) systemic tx and avelumab 1L maintenance (1LM): Results from the IMPACT UC-III study.

390 Background: Avelumab 1LM is a standard of care for pts with mUC that has not progressed after 1L platinum-based chemotherapy (PBC). Immuno-oncology (IO) monotherapy is considered in pts with mUC who are ineligible to receive PBC. Recently approved 1L tx options include enfortumab vedotin + pembrolizumab and nivolumab + gemcitabine/cisplatin. This US retrospective study examined pt characteristics, tx patterns, and clinical outcomes among pts with mUC receiving 1L tx, including avelumab 1LM. Methods: Pts with mUC (bladder cancer; stage IIIB or IV, or ≥2 claims with ICD-10 diagnoses for metastatic cancer) aged ≥18 years, who initiated 1L tx (index date) from Jan 1, 2020 to Jul 31, 2023, were identified from the Healthcare Integrated Research Database (HIRD®; claims and clinical data from the health plan’s Cancer Care Quality Program). Clinical outcomes, including time to next tx (TTNT; time from 1L tx initiation to second-line tx) and overall survival (OS), were evaluated post index date. Pt characteristics and tx patterns were summarized using descriptive statistics. Avelumab 1LM use was identified on/after June 30, 2020 and ≤90 d after 1L PBC discontinuation. OS from the start of 1L tx or 1LM was analyzed using Kaplan-Meier methodology. Results: Of 2,820 pts with mUC, 1L tx was PBC in 37.0% (n=1,044), IO monotherapy in 39.0% (n=1,099), and other tx in 24.0% (n=677; antibody-drug conjugates and non-PBC). Among pts who received 1L PBC, 15.0% (n=157) initiated avelumab 1LM within 90 days of completing 1L PBC. Avelumab uptake in 2020-2023 by year was 10.8% (Jun-Dec 2020), 29.9%, 34.4%, and 24.8% (Jan-Aug 2023), respectively; 38.9% of pts were still receiving avelumab at the end of the study period. In the 1L PBC and IO cohorts, mean age (SD) was 65.5 (11.1) and 74.6 (10.7) years, respectively. 60% of pts were male. In the 1L PBC and 1L IO monotherapy cohorts, respectively, median follow-up (IQR) was 11.2 (5.6-20.3) and 8.6 (4.0-17.7) months (mo); median TTNT (IQR) was 4.8 (2.8-8.3) and 5.5 (2.8-11.0) mo; and median OS (95% CI) was 29.7 (25.1-37.2) and 20.0 (17.1-25.6) mo. In pts who received avelumab 1LM, median follow-up (IQR) from start of 1L PBC was 14.6 (9.2-21.3) mo; median TTNT (IQR) was 7.6 (6.2-12.3) mo; median time on avelumab tx was 5.0 (1.8-10.2) mo; and 1- and 2-year OS rates, respectively, from start of avelumab 1LM were 78% and 65%, and from start of 1L PBC were 84% and 68% (median OS was not estimable because >50% of pts remained alive at the end of the study period). Conclusions: Despite advances in 1L tx for mUC, IO monotherapy remains a prevailing option for older, commercially insured patients in the US. In this descriptive rw study, pts treated with 1L PBC had longer OS than pts treated with 1L IO monotherapy. Future studies with longer follow-up are needed to further evaluate pt outcomes.