This phase II trial investigates how well the addition of olaparib following completion of surgery and chemotherapy works in treating patients with pancreatic cancer that has been surgically removed (resected) and has a pathogenic mutation in BRCA1, BRCA2, or PALB2. Olaparib is an inhibitor of PARP, an enzyme that helps repair deoxyribonucleic acid (DNA) when it becomes damaged. Blocking PARP may help keep tumor cells from repairing their damaged DNA, causing them to die. PARP inhibitors are a type of targeted therapy.

This phase II trial studies the effect of capecitabine and temozolomide after surgery in treating patients with high-risk well-differentiated pancreatic neuroendocrine tumors. Chemotherapy drugs, such as capecitabine and temozolomide, work in different ways to stop the growth of tumor cells, either by killing the cells, by stopping them from dividing, or by stopping them from spreading. Giving capecitabine and temozolomide after surgery could prevent or delay the return of cancer in patients with high-risk well-differentiated pancreatic neuroendocrine tumors.