Testing the Addition of Pembrolizumab, an Immunotherapy Cancer Drug to Olaparib Alone as Therapy for Patients With Pancreatic Cancer That Has Spread With Inherited BRCA Mutations

PRIMARY OBJECTIVE: I. To evaluate the progression free survival (PFS) of advanced pancreatic cancer patients with germline BRCA1 or BRCA2 mutations treated with olaparib + pembrolizumab compared to olaparib alone as maintenance therapy. SECONDARY OBJECTIVES: I. To evaluate the safety and tolerability associated with the combination of olaparib + pembrolizumab versus (vs.) olaparib alone as maintenance therapy. II. To evaluate the overall survival (OS) of patients treated with olaparib + pembrolizumab compared to olaparib alone as maintenance therapy. III. To evaluate the overall response rate (ORR) by Response Evaluation Criteria in Solid Tumors (RECIST) 1.1, including confirmed and unconfirmed, complete and partial response, of patients treated with olaparib + pembrolizumab compared to olaparib alone, in the subset of patients with measurable disease. IV. To evaluate the duration of response (DoR) by RECIST 1.1 in patients treated with olaparib + pembrolizumab compared to olaparib alone. BANKING OBJECTIVE: I. To bank tissue and blood specimens for future correlative studies. OUTLINE: Patients are randomized to 1 of 2 arms. ARM A: Patients receive olaparib orally (PO) twice daily (BID) on days 1-21 and pembrolizumab intravenously (IV) over 30 minutes on day 1 of each cycle. Treatment repeats every 21 days for up to 18 cycles in the absence of disease progression or unacceptable toxicity. Beginning in cycle 19, patients receive olaparib PO BID on days 1-42 and pembrolizumab IV over 30 minutes on day 1 of each cycle. Cycles repeat every 42 days in the absence of disease progression or unacceptable toxicity. ARM B: Patients receive olaparib PO BID on days 1-21 of each cycle. Cycles repeat every 21 days in the absence of disease progression or unacceptable toxicity. Patients undergo computed tomography (CT) scan or magnetic resonance imaging (MRI), tumor biopsy and blood sample collection throughout the study. After completion of study treatment, patients are followed for 30 days and every 6 months for 3 years from the date of randomization.