A Study of Niraparib in Combination With Abiraterone Acetate and Prednisone Versus Abiraterone Acetate and Prednisone for the Treatment of Participants With Deleterious Germline or Somatic Homologous Recombination Repair (HRR) Gene-MutatedProstatic Neoplasms (mCSPC)

rPFS: time interval from date of randomization to first date of radiographic progression as assessed by investigator or death due to any cause, whichever occurred first. rPFS was determined by: (1) progression of soft tissue lesions measured by computerized tomography (CT) or magnetic resonance imaging (MRI) per response evaluation criteria in solid tumors (RECIST) 1.1; (2) progression of bone lesions observed by bone scan per prostate cancer working group 3 (PCWG3) criteria: bone progression was confirmed by subsequent scan greater than or equal to (>=) 6 weeks later. Week 8 scan was baseline to which all subsequent scans were compared to determine progression. A confirmatory scan with >=2 new lesions indicated progression; A confirmatory scan not showing >=2 new lesions means no progression. If Week 8 scan shows <2 new bone lesions compared to baseline, first scan with >=2 new lesions compared to Week 8 scan indicated progression, when confirmed by a subsequent scan >=6 weeks later.

rPFS: time interval from date of randomization to first date of radiographic progression as assessed by investigator or death due to any cause, whichever occurred first. rPFS was determined by: (1) progression of soft tissue lesions measured by CT or MRI per RECIST 1.1; (2) progression of bone lesions observed by bone scan per PCWG3 criteria: bone progression was confirmed by subsequent scan >= 6 weeks later. Week 8 scan was baseline to which all subsequent scans were compared to determine progression. A confirmatory scan with >=2 new lesions indicated progression; A confirmatory scan not showing >=2 new lesions means no progression. If Week 8 scan shows <2 new bone lesions compared to baseline, first scan with >=2 new lesions compared to Week 8 scan indicated progression, when confirmed by a subsequent scan >=6 weeks later.

rPFS: time interval from date of randomization to first date of radiographic progression as assessed by investigator or death due to any cause, whichever occurred first. rPFS was determined by: (1) progression of soft tissue lesions measured by CT or MRI per RECIST 1.1; (2) progression of bone lesions observed by bone scan per PCWG3 criteria: bone progression was confirmed by subsequent scan >= 6 weeks later. Week 8 scan was baseline to which all subsequent scans were compared to determine progression. A confirmatory scan with >=2 new lesions indicated progression; A confirmatory scan not showing >=2 new lesions means no progression. If Week 8 scan shows <2 new bone lesions compared to baseline, first scan with >=2 new lesions compared to Week 8 scan indicated progression, when confirmed by a subsequent scan >=6 weeks later.

Time to symptomatic progression was defined as time from the date of randomization to the date of any of the following (whichever occurred first): (a) the use of external beam radiation therapy for skeletal or pelvic symptoms, (b) the need for tumor-related orthopedic surgical intervention, (c) other cancer-related procedures (example: nephrostomy insertion, bladder catheter insertion, external beam radiation therapy, or surgery for tumor symptoms), (d) cancer-related morbid events (that is, fracture [symptomatic and/or pathologic], cord compression, urinary obstructive events), (e) initiation of a new systemic anti-cancer therapy because of cancer symptoms.

Time to symptomatic progression was defined as time from the date of randomization to the date of any of the following (whichever occurred first): (a) the use of external beam radiation therapy for skeletal or pelvic symptoms, (b) the need for tumor-related orthopedic surgical intervention, (c) other cancer-related procedures (example: nephrostomy insertion, bladder catheter insertion, external beam radiation therapy, or surgery for tumor symptoms), (d) cancer-related morbid events (that is, fracture [symptomatic and/or pathologic], cord compression, urinary obstructive events), (e) initiation of a new systemic anti-cancer therapy because of cancer symptoms.

Time to symptomatic progression was defined as time from the date of randomization to the date of any of the following (whichever occurred first): (a) the use of external beam radiation therapy for skeletal or pelvic symptoms, (b) the need for tumor-related orthopedic surgical intervention, (c) other cancer-related procedures (example: nephrostomy insertion, bladder catheter insertion, external beam radiation therapy, or surgery for tumor symptoms), (d) cancer-related morbid events (that is, fracture [symptomatic and/or pathologic], cord compression, urinary obstructive events), (e) initiation of a new systemic anti-cancer therapy because of cancer symptoms.