Azacitidine With or Without Nivolumab or Midostaurin, or Decitabine and Cytarabine Alone in Treating Older Patients With Newly Diagnosed Acute Myeloid Leukemia or High-Risk Myelodysplastic Syndrome

Inclusion Criteria: * REGISTRATION STEP 1-SPECIMEN SUBMISSION * Patients must be suspected to have previously untreated acute myelogenous leukemia (AML) or myelodysplastic syndrome with excess blasts-2 (MDS-EB-2) * Patients must not be known to have AML in the central nervous system (CNS) * Patients must have specimens submitted for FLT3 testing for randomization stratification; collection of pretreatment specimens must be completed within 1 day of registration to Step 1; specimens must be submitted via the Southwest Oncology Group (SWOG) Specimen Tracking System; FLT3 results will be used for stratification purposes at the time of randomization; E-mail notification of randomization assignment must be received prior to Step 2 registration * Patients must be offered participation in specimen banking; with patient consent, pretreatment specimens must be collected and submitted via the SWOG Specimen Tracking System * Patients who have received prior therapy with midostaurin, any anti-PD-1 or anti-PD-L1 therapy, any deoxyribonucleic acid (DNA)-methyltransferase inhibitor (including hypomethylating agents such as azacitidine, decitabine, or other investigational agent that acts by inhibiting DNA or ribonucleic acid \[RNA\] methylation) for any condition, or prior intensive cytotoxic therapy for myelodysplastic syndrome (MDS), are not eligible * Patients must be able to swallow oral medications without crushing or chewing * Prior malignancy is allowed providing it does not require…