PLX3397, Radiation Therapy, and Antihormone Therapy in Treating Patients With Intermediate- or High-Risk Prostate Cancer

PRIMARY OBJECTIVES: I. To conduct a phase I, dose escalation trial with a primary objective of establishing the maximum tolerated dose (MTD) and the dose limiting toxicity (DLT). SECONDARY OBJECTIVES: I. To assess the effects of radiation therapy (RT), androgen deprivation therapy (ADT), and PLX3397 (at its MTD) on tumor-associated macrophages (TAMs) in the prostate biopsy after treatment. OUTLINE: This is a dose-escalation study of multitargeted tyrosine kinase inhibitor PLX3397. Patients receive multitargeted tyrosine kinase inhibitor PLX3397 orally (PO) twice daily (BID) for 6 months, undergo radiation therapy for 2 months daily (Monday-Friday) beginning at month 3, and undergo ADT with leuprolide acetate, goserelin acetate, or degarelix injections in any month. After completion of study treatment, patients are followed up at 20-30 days and then every 12 weeks thereafter.