The Combination of Anti-PD-1 With Radiotherapy in Previously Untreated Metastatic Melanoma

Inclusion Criteria: * 1\. Subject has provided informed consent prior to initiation of any study-specific activities/procedures * 2\. Male or female age \> 20 years at the time of informed consent * 3\. Histologically confirmed diagnosis of unresectable stage III or IV melanoma as per AJCC staging system 8th edition * 4\. Subject with no prior systemic treatment * 5\. Eastern Cooperative Oncology Group (ECOG) Performance Status \< 1 * 6\. Screening labs performed within 7 days of randomization demonstrating adequate hematologic, coagulation, liver, and kidney functions * 7\. Indications for radiotherapy * 8\. BRAF status must be checked, but patient is eligible regardless of BRAF mutations (BRAF V600 wild type or BRAF V600 mutation positive are both eligible) Exclusion Criteria: * 1\. Ocular melanoma * 2\. Active brain metastasis (stable after 1 month of radiotherapy, gamma knife surgery or surgery) * 3\. Requires palliative radiotherapy * 4\. Previous treatment with chemotherapy, a CTLA-4 or PD-1/PD-L1 antagonist agent, including treatment in adjuvant setting * 5\. Autoimmune disease requiring chronic treatment with systemic corticosteroids or any other immunosuppressive agents 7 days prior to inclusion. (physiologic dose of prednisolone 10mg or equivalent are accepted) * 6\. Concurrent medical disease which would significantly limit full compliance with the study such as, but not limited to the following: heart failure (III, IV as per NYHA classification), renal insufficiency, active infection (requires negative gest for clinically suspected HIV, hepatitis B virus, hepatitis C virus). If positive results are not indicative of true active or chronic infection, the subject may enter the study after discussion and agreement between the investigator and medical director. * 7\. Has known malignancy that is progressing and requires active treatment * 8\. Has known psychiatric or substance abuse disorders that would interfere with cooperation requirements of the trial * 9\. Lack of availability for clinical follow-up assessments