Radiation Therapy, Plasma Exchange, and Immunotherapy (Pembrolizumab or Nivolumab) for the Treatment of Melanoma

PRIMARY OBJECTIVE: I. To determine the kinetics of soluble (s)PD-L1 removal and regeneration by plasma exchange in patients with melanoma. SECONDARY OBJECTIVES: I. To observe response at 3 months after plasma exchange plus immunotherapy. II. To observe ongoing response at approximate 3 month intervals after plasma exchange plus immunotherapy. CORRELATIVE RESEARCH OBJECTIVES: I. To determine the effects of plasma exchange on immune cell function. II. To observe the kinetics of extracellular vesicles (EVs) after plasma exchange in patients with melanoma. OUTLINE: Patients undergo radiation therapy daily on days 1-5 (weekdays). Patients then undergo therapeutic plasma exchange over 1-2 hours on the first session starting on the last day of radiation therapy and the last session ending prior to immunotherapy. Beginning day 5, patients receive pembrolizumab intravenously (IV) or nivolumab IV. Treatment with pembrolizumab continues every 3 weeks or treatment with nivolumab continues every 2 weeks in the absence of disease progression or unacceptable toxicity. Patients also undergo blood sample collection throughout the study and standard of care (SOC) computed tomography (CT), positron emission tomography (PET), and/or magnetic resonance imaging (MRI) scans as clinically indicated during follow-up. After completion of study treatment, patients are followed up at 3 weeks and then for up to 2 years.