Testing the Addition of an Anticancer Drug, Olaparib, to the Usual Chemotherapy (Temozolomide) for Advanced Neuroendocrine Cancer

Inclusion Criteria: * Documentation of disease * Histologic documentation: Histologically-proven advanced (metastatic or unresectable primary) pheochromocytoma or paraganglioma * Stage: Advanced (metastatic or unresectable primary) disease * Tumor site: Histologically-proven pheochromocytoma or paraganglioma * Radiographic evaluation: Radiographic evidence of disease progression by Response Evaluation Criteria in Solid Tumors (RECIST) version (v) 1.1 in the 12 months prior to registration * Measurable disease * Lesions must be accurately measured in at least one dimension (longest diameter to be recorded) as \>= 1 cm with CT or MRI (or \>= 1.5 cm for lymph nodes). Non-measurable disease includes disease smaller than these dimensions or lesions considered truly non-measurable including: leptomeningeal disease, ascites, pleural or pericardial effusion, lymphangitic involvement of skin or lung * Prior treatment with other somatostatin analog, chemotherapy, radiotherapy (including peptide radionuclide receptor therapy \[PRRT\]), or surgery must be completed \>= 28 days prior to registration. Patients must have recovered from any effects of any major surgery prior to registration * Prior treatment with radiolabeled metaiodobenzylguanidine (MIBG) must be completed \>= 12 weeks prior to registration and lifetime cumulative 131I-MIBG dose must be \< 1000 MBq kg\^-1 (36 mCi kg\^-1) * Prior treatment with antibiotics must be completed \>= 7 days prior to registration * No …