A stratified phase I dose escalation trial of hypofractionated radiotherapy followed by ipilimumab in metastatic melanoma: long-term follow-up and final outcomes

• Main Authors: Amit Maity, Rosemarie Mick, Ramesh Rengan, Tara C. Mitchell, Ravi K. Amaravadi, Lynn M. Schuchter, Daniel A. Pryma, Dana M. Patsch, Alisha P. Maity, Andy J. Minn, Robert H. Vonderheide, John N. Lukens
• Format: Article
• Language: English
• Published: Taylor & Francis Group 2021-01-01
• Series: OncoImmunology
• Subjects: ctla-4; ipilimumab; radiation; abscopal; hypofractionated radiation
• Online Access: http://dx.doi.org/10.1080/2162402X.2020.1863631

We conducted a phase I dose-escalation trial of radiation with ipilimumab in patients with melanoma with ≥2 metastatic lesions. Here, we report the final full clinical analysis. Patients received RT (6 or 8 Gy x 2 or 3 doses) to a single lesion followed by 4 cycles of ipilimumab. The primary endpoint was maximum tolerated dose of RT, and secondary endpoint was response at non-radiated sites. Twenty-two patients with treatment-naïve (n = 11) or treatment-refractory (n = 11) Stage IV melanoma were enrolled. There were 31 treatment-related adverse events (AEs), of which 16 were deemed immune-related. Eleven patients had grade 3 AEs (no grade 4/5). There were no dose-limiting toxicities related to the radiation/ipilimumab combination. Five of 22 patients (22.7%, 95% CI 7.8–45.4%) had partial response as best response and three (13.6%) had stable disease. Median overall survival was 10.7 months (95% CI, 4.9 months to not-estimable) and median progression-free survival 3.6 months (95% CI, 2.9 months to 7.8 months). Seven patients were still alive at the time of last follow-up (median follow-up 89.2 months), most of whom received pembrolizumab after progression. Radiotherapy followed by ipilimumab was well tolerated and yielded a response rate that compares favorably to the objective response rate with ipilimumab alone. Furthermore, 32% of patients are long-term survivors, most of whom received pembrolizumab. Based on these results, the recommended dose that was used in subsequent Phase 2 trials was 8 Gy x 3 doses. Clinical Trial Registration: NCT01497808 (www.clinicaltrials.gov)