Testing the Use of the Combination of Selumetinib and Olaparib or Selumetinib Alone Targeted Treatment for RAS Pathway Mutant Recurrent or Persistent Ovarian and Endometrial Cancers, A ComboMATCH Treatment Trial

Inclusion Criteria: * Patient must have enrolled onto EAY191 and must have been given a treatment assignment to ComboMATCH to EAY191-N4 based on the presence of an actionable mutation as defined in EAY191 * Patients must be enrolled on the ComboMATCH Master Registration Trial EAY191 * Patients must have RAS pathway mutations as determined by the ComboMATCH screening assessment * Cohort 1: Patients with histologically confirmed RAS pathway mutant ovarian, primary peritoneal, or fallopian tube ("ovarian") cancer (activating mutations in KRAS, NRAS, HRAS, BRAF, MEK1, MEK2, or inactivating mutations in NF1) * Cohort 2: Patients with histologically confirmed RAS pathway mutant endometrial cancer (activating mutations in KRAS, NRAS, HRAS, BRAF, MEK1, MEK2, or inactivating mutations in NF1) * Patients must have disease that can be safely biopsied and agree to a pre-treatment biopsy or, if disease cannot be safely biopsied, have archival tissue available from within 12 months prior to the date of registration on the ComboMATCH Registration Trial (EAY191) * Patients must have progressed after first-line treatment for recurrent or persistent disease * Patients with ovarian cancer should not be eligible for further platinum-based therapy * Patients with endometrial cancer must have received or been offered an immune oncology agent (alone or in combination with lenvatinib) unless there are existing contraindications for immune oncology agents or lenvatinib * Patients may have recei…