Study Comparing Orteronel Plus Prednisone in Participants With Chemotherapy-Naive Metastatic Castration-Resistant Prostate Cancer

rPFS was defined as the time from randomization to the first objective evidence of radiographic disease progression assessed by independent central radiology review or death due to any cause, whichever occurred first. Radiographic disease progression was evaluated by computerized tomography (CT) scan or magnetic resonance imaging (MRI) and radionuclide bone scans at regularly scheduled visits. Radiographic disease progression in bone required a confirmatory scan. Radiographic disease progression in soft tissue did not require a confirmatory scan for purposes of analysis. Radiographic disease progression was evaluated by independent central radiology review using Response Evaluation Criteria In Solid Tumors (RECIST) 1.1 for soft tissue disease and Prostate Cancer Working Group (PCWG2) guidelines for bone disease. Participants who did not reach the endpoint were censored at their last assessment.

Overall survival was calculated from the date of participant randomization to the date of participant death due to any cause. Participants without documentation of death at time of the analysis were censored as of the date the participant was last known to be alive, or the data cutoff date, whichever was earlier.

The PSA50 is defined as a decline of at least 50 percent (%) from baseline.

A favorable CTC count was defined as less than <5 counts per 7.5 milliliter (mL) in whole blood. An unfavorable CTC count was defined as greater than or equal to (>=) 5 counts/7.5 mL in whole blood.

Time to pain progression was defined as the time from participant randomization to the first assessment date of pain progression. Pain progression was defined as the occurrence of 1 of the following and confirmed by an additional assessment, at least 3 weeks but not more than 5 weeks later: The brief pain inventory-short form (BPI-SF) worst pain score was >=4 with a >=2 point increase over baseline in BPI-SF worst pain score with stable or increased analgesic use; The BPI-SF worst pain score was >=4 but not less than baseline with new or increased (relative to baseline) Step II or Step III analgesic use; The BPI-SF worst pain score was <=3 but not less than baseline with new or increased (relative to baseline) Step III analgesic use. BPI-SF was an 11-item questionnaire, designed to assess severity and impact of pain on daily functions. Total score ranged from 0 to 100 with lower scores being indicative of less pain or pain interference.

Grade 3 (Severe) events=unacceptable or intolerable events, significantly interrupting usual daily activity, require systemic drug therapy/other treatment. Grade 4 (Life-threatening) events caused participant to be in imminent danger of death. Grade 5 (Death) events=death related to an AE.

ECOG assessed participant's performance status on 5 point scale: 0=Fully active/able to carry on all pre-disease activities without restriction; 1=restricted in physically strenuous activity, ambulatory/able to carry out light or sedentary work; 2=ambulatory (>50 percent of waking hours [hrs]), capable of all self care, unable to carry out any work activities; 3=capable of only limited self care, confined to bed/chair >50 percent of waking hrs; 4=completely disabled, cannot carry on any self care, totally confined to bed/chair; 5=dead. Worst change was defined as the worst overall change that occurred in ECOG status at any measured time point during the treatment period.

Worst change was defined as the worst overall change that occurred in cardiac ejection fraction at any measured time point.

Skeletal related (SRE) event is defined as a fracture or spinal cord compression or the need for radiation or surgery at the site of a prostate cancer metastatic lesion that is substantiated by radiographic or pathologic evidence.

Time to SRE is defined as the time from randomization to SRE, or death due to any cause, whichever comes first. SRE is defined as a fracture or spinal cord compression or the need for radiation or surgery at the site of a prostate cancer metastatic lesion that is substantiated by radiographic or pathologic evidence.

The PSA50 is defined as a decline of PSA by 50 percent from baseline.

The PSA90 is defined as a decline of PSA by 90 percent from baseline.

The PSA90 is defined as a decline of PSA by 90 percent from baseline.

Time to PSA progression was defined as time from randomization to a PSA increase of 25 percent and PSA rise of at least 2 nanogram per milliliter (ng/mL) above the lowest value observed post baseline or, if no PSA decline occurred post baseline, compared to baseline PSA.

Time to docetaxel based chemotherapy is defined as the time from randomization to the start of docetaxel based chemotherapy for prostate cancer, regardless of whether the participant received concurrent orteronel or not. Deaths due to disease progression prior to Docetaxel based chemotherapy were considered as events.

Time to subsequent antineoplastic therapy is defined as the time from randomization to the start of any alternate antineoplastic therapy for prostate cancer. Deaths due to disease progression prior to antineoplastic therapy for prostate cancer are considered as events. Otherwise, time to next therapy is censored at the date of death or the last date the participant was known to be alive or the data cutoff date, whichever is earlier.

Percentage of participants with objective response based assessment of confirmed complete response (CR) or confirmed partial response (PR) according to RECIST 1.1. A CR was defined as the disappearance of all target lesions determined by computerized tomography (CT) or MRI. Any pathological lymph nodes (whether target or non-target) must have had reduction in short axis to <10 millimetre (mm). A PR was defined as at least a 30% decrease in the sum of diameters of target lesions, taking as reference the baseline sum of longest diameters of non-lymph node lesions and of the short diameter or short axis of lymph nodes.

Global health status deterioration is defined as a drop greater than 16 points from the baseline assessment, confirmed at least 3 weeks later, on the European Organization for Research and Treatment of Cancer Quality of Life Questionnaire Core Module 30 (EORTC QLQ-C30) index after the score has been linearly transformed to a 0 to 100 scale. EORTC QLQ-C30 consists of 30 questions, where question 1 to 28 can be answered with 1: Not at all, 2: A little, 3: Quite a bit, 4: Very much and question 29 to 30 with 1: Very poor to 7: Excellent. For subscales a high score from 0-100 indicates: high global quality of life, high level of functioning (physical, role, emotional, cognitive, social) or a high level of symptoms (fatigue, nausea, pain, dyspnea, insomnia, appetite loss, constipation, diarrhoea, financial difficulties).