Testing Olaparib and Temozolomide Versus the Usual Treatment for Uterine Leiomyosarcoma After Chemotherapy Has Stopped Working

Inclusion Criteria: * Histologically confirmed leiomyosarcoma of uterine origin, as established by the site institutional practice for pathology confirmation for research studies when enrolling the patient on study. Central pathology review will not occur. * Metastatic or locally advanced and surgically unresectable disease, in the opinion of the treating investigator. * Patients must have at least one lesion that is measurable per Response Evaluation Criteria in Solid Tumors (RECIST) version (v)1.1 criteria to be eligible for the study. * Not pregnant and not nursing, because this study involves agents that have known genotoxic, mutagenic and teratogenic effects. Therefore, for women of childbearing potential only, a negative pregnancy test done =\< 7 days prior to registration is required * Age \>= 18 years. * Eastern Cooperative Oncology Group (ECOG) Performance Status =\< 2. * Patients must have had prior progression on, or intolerance to, at least two prior lines of systemic therapy for advanced uLMS, one of which was an anthracycline (anthracycline monotherapy or combination). Adjuvant chemotherapy will qualify as a prior line of treatment. Endocrine treatment will not qualify as a prior line of treatment. * Patients may not have received prior treatment with any PARP inhibitor, temozolomide or dacarbazine (IV analogue of temozolomide). * Patients may not have had prior treatment with BOTH of the agents included on the investigator's choice arm: trabectedin AND pazopan…