Safety Analysis of Co-Administration of Radiation Therapy with Enfortumab Vedotin Based Regimens in Metastatic Urothelial Carcinoma

Introduction/Background: Enfortumab vedotin (EV) and pembrolizumab (P) is the standard of care for patients with locally advanced or metastatic urothelial carcinoma (la/mUC). Because radiation (RT) is frequently used for symptom palliation, we examined the safety of co-administering EV with RT. Materials and Methods: This single institution retrospective study selected patients with la/mUC, who received at least 1 dose of EV and initiated RT to any site within 30 days of each other. Patient characteristics, number of EV cycles received, the location of irradiated sites, RT dose/delivery approach, severity/type of radiation treatment-related adverse events (TRAEs), and symptom response after RT were recorded. The primary aim of this study was to examine radiation TRAEs, with severity graded using the CTCAE version 5.0 classification. Results: Nine patients with 15 irradiated metastasis met eligibility criteria. The median radiation dose and cycles of EV were 30 Gy and 5 cycles respectively. Patients only experienced acute grade 1 or 2 TRAEs including fatigue, nausea, and dermatitis without desquamation. Chronic treatment-related toxicity was noted in 2 patients, which were grade 1 neck pain and 2 fatigue. All patients demonstrated some degree of symptom relief and four experienced complete resolution of their cancer-related symptoms at the irradiated site. One patient with limited disease burden completed stereotactic body radiation therapy and remains disease free 6 months after discontinuing all treatment. Conclusion: This study demonstrates that co-administration of RT with EV-based regimens could be safe and effective for symptom palliation. Larger series examining this treatment combination are needed.