Site-specific response patterns, pseudoprogression, and acquired resistance in patients with melanoma treated with ipilimumab combined with anti–PD-1 therapy

Abstract

Background: Patients with metastatic melanoma have variable responses to combination ipilimumab and nivolumab. The objectives of this study were to examine the patterns of response and survival in patients treated with combination ipilimumab and anti–PD-1 therapy (IPI + PD1) and to explore the nature of pseudoprogression and acquired resistance. Methods: Patients with metastatic melanoma who received treatment with first-line IPI + PD1 had all metastases ≥5 mm measured on computed tomography/magnetic resonance imaging studies. The lesional response rate (LRR) and the overall response rate (ORR) were determined according to Response Evaluation Criteria in Solid Tumors, version 1.1. Results: In total, 140 patients who had 833 metastases were studied. The ORR and the overall complete response (CR) rate decreased as tumor burden or the number of metastases increased. Metastases that had a CR (49%) were smaller than metastases without a CR (median, 13 vs 17 mm; P