Testing the Addition of a New Anti-Cancer Drug, Niraparib, to the Usual Treatment (Hormone and Radiation Therapy) for Prostate Cancer With a High Chance of Recurring

PRIMARY OBJECTIVES: I. To establish the preferred dose of niraparib in combination with radiation and antiandrogen therapy (ADT). (Phase I) II. To compare the disease-free state, defined as prostate specific antigen (PSA) remaining \< 0.1 ng/ml at the end of ADT therapy in men with high risk prostate cancer treated with standard therapy with or without the addition of niraparib. (Phase IIR) SECONDARY OBJECTIVES: I. To further establish the safety and toxicity profile of standard treatment with radiation and androgen deprivation therapy specifically, two years from initiation of ADT, plus niraparib at the phase II dose. II. To compare the overall survival, prostate cancer-specific survival, local/regional or distant progression, and distant metastatic disease rates of standard therapy with or without the addition of niraparib. EXPLORATORY OBJECTIVE: I. To identify genomic biomarkers of response to combination therapy with radiation, ADT and PARP inhibition. OUTLINE: This is a phase I, dose-escalation study of niraparib, followed by a randomized phase II study. PHASE I: Patients receive niraparib orally (PO) once daily (QD) and receive standard of care gonadotrophin releasing hormone (GnRH) agonist androgen suppression therapy. Treatment with niraparib continues for 12 months, and GnRH agonist therapy for 24 months in the absence of disease progression or unacceptable toxicity. Beginning 8 weeks after starting niraparib and GnRH agonist, patients undergo standard of care intensity-modulated radiation therapy (IMRT) 5 days per week for about 6-9 weeks, depending on type of radiation therapy given, in the absence of disease progression or unacceptable toxicity. Patients also undergo magnetic resonance imaging (MRI) on study. PHASE II: Patients are randomized to 1 of 2 arms: ARM I: Patients undergo standard of care GnRH agonist androgen suppression therapy for 24 months in the absence of disease progression or unacceptable toxicity. Beginning 8-28 weeks after starting GnRH agonist, patients undergo IMRT 5 days per week for about 6-9 weeks depending on type of radiation therapy given in the absence of disease progression or unacceptable toxicity. Patients also undergo MRI on study. ARM II: Patients undergo standard of care GnRH agonist androgen suppression therapy for 24 months, and niraparib PO QD for 12 months in the absence of disease progression or unacceptable toxicity. Beginning 8 weeks after starting niraparib, patients undergo standard of care IMRT 5 days per week for about 6-9 weeks depending on type of radiation therapy given in the absence of disease progression or unacceptable toxicity. Patients also undergo MRI on study. After completion of study treatment, patients are followed up every 6 months for 3 years, then annually for 3 years.