Summary
This is a phase I-II trial to find the safety and activity of adding a new drug (neratinib) to the usual treatment (radiation combined with male hormone deprivation therapy) in lowering the chance of prostate cancer growing or returning. Niraparib is an inhibitor of PARP, an enzyme that helps repair deoxyribonucleic acid (DNA) when it becomes damaged. Blocking PARP may help keep cancer cells from repairing their damaged DNA, causing them to die. PARP inhibitors are a type of targeted therapy. Adding niraparib to the usual care may lower the chance of prostate cancer growing or returning.