A Study to Compare the Administration of Pembrolizumab After Surgery Versus Administration Both Before and After Surgery for High-Risk Melanoma

PRIMARY OBJECTIVE: I. To compare event-free survival (EFS) in participants with high-risk resectable melanoma randomized to neoadjuvant pembrolizumab (MK-3475) with participants randomized to adjuvant pembrolizumab (MK-3475). SECONDARY OBJECTIVES: I. To assess the frequency and severity of toxicities on each of the arms. II. To compare between arms overall survival (OS), disease control at 24 weeks, locoregional control in the surgical site(s), and total number of pembrolizumab (MK-3475) doses received. III. On the neoadjuvant arm, to estimate the pathologic response rate, the Response Evaluation Criteria in Solid Tumors (RECIST) 1.1 response rate (confirmed and unconfirmed complete response \[CR\] and partial response \[PR\]), and the immune-related (i)RECIST response rate (confirmed and unconfirmed CR and PR), before surgical resection; to compare definitions of pathologic partial response; and to evaluate the association between pathologic response and EFS and OS. IV. To describe the proportion of participants on each arm who received the surgery planned at randomization. ADDITIONAL OBJECTIVE: I. To bank tumor tissue and whole blood in anticipation of future correlative studies in this participant population. OUTLINE: Patients are randomized to 1 of 2 arms. ARM I: Within 17 days (preferably within 14 days) days after surgical resection, patients receive pembrolizumab intravenously (IV) over 30 minutes on day 1. Treatment repeats every 3 weeks for 18 cycles in the absence of disease progression or unacceptable toxicity. Patients also undergo collection of blood throughout the study, and magnetic resonance imaging (MRI) or computers tomography (CT) on study. ARM II: Patients receive pembrolizumab IV over 30 minutes on day 1 every 3 weeks for 3 cycles, then undergo surgical resection within 3 weeks. Within 84 days, patients receive pembrolizumab IV over 30 minutes every 3 weeks for 15 cycles in the absence of disease progression or unacceptable toxicity. Patients also undergo collection of blood throughout the study and MRI or CT on study. After completion of study treatment, patients are followed up at 3 and 12 weeks, then every 3 months for 2 years, every 6 months for 3 years, then every 12 months for up to 10 years.