Paul N. Mainwaring

Abiraterone and Increased Survival in Metastatic Prostate Cancer

BACKGROUND Biosynthesis of extragonadal androgen may contribute to the progression of castration-resistant prostate cancer. We evaluated whether abiraterone acetate, an inhibitor of androgen biosynthesis, prolongs overall survival among patients with metastatic castration-resistant prostate cancer who have received chemotherapy. METHODS We randomly assigned, in a 2:1 ratio, 1195 patients who had previously received docetaxel to receive 5 mg of prednisone twice daily with either 1000 mg of abiraterone acetate (797 patients) or placebo (398 patients). The primary end point was overall survival. The secondary end points included time to prostate-specific antigen (PSA) progression (elevation in the PSA level according to prespecified criteria), progression-free survival according to radiologic findings based on prespecified criteria, and the PSA response rate. RESULTS After a median follow-up of 12.8 months, overall survival was longer in the abiraterone acetate-prednisone group than in the placebo-prednisone group (14.8 months vs. 10.9 months; hazard ratio, 0.65; 95% confidence interval, 0.54 to 0.77; P<0.001). Data were unblinded at the interim analysis, since these results exceeded the preplanned criteria for study termination. All secondary end points, including time to PSA progression (10.2 vs. 6.6 months; P<0.001), progression-free survival (5.6 months vs. 3.6 months; P<0.001), and PSA response rate (29% vs. 6%, P<0.001), favored the treatment group. Mineralocorticoid-related adverse events, including fluid retention, hypertension, and hypokalemia, were more frequently reported in the abiraterone acetate-prednisone group than in the placebo-prednisone group. CONCLUSIONS The inhibition of androgen biosynthesis by abiraterone acetate prolonged overall survival among patients with metastatic castration-resistant prostate cancer who previously received chemotherapy. (Funded by Cougar Biotechnology; COU-AA-301 ClinicalTrials.gov number, NCT00638690.).

Abiraterone in Metastatic Prostate Cancer without Previous Chemotherapy

BACKGROUND Abiraterone acetate, an androgen biosynthesis inhibitor, improves overall survival in patients with metastatic castration-resistant prostate cancer after chemotherapy. We evaluated this agent in patients who had not received previous chemotherapy. METHODS In this double-blind study, we randomly assigned 1088 patients to receive abiraterone acetate (1000 mg) plus prednisone (5 mg twice daily) or placebo plus prednisone. The coprimary end points were radiographic progression-free survival and overall survival. RESULTS The study was unblinded after a planned interim analysis that was performed after 43% of the expected deaths had occurred. The median radiographic progression-free survival was 16.5 months with abiraterone-prednisone and 8.3 months with prednisone alone (hazard ratio for abiraterone-prednisone vs. prednisone alone, 0.53; 95% confidence interval [CI], 0.45 to 0.62; P<0.001). Over a median follow-up period of 22.2 months, overall survival was improved with abiraterone-prednisone (median not reached, vs. 27.2 months for prednisone alone; hazard ratio, 0.75; 95% CI, 0.61 to 0.93; P=0.01) but did not cross the efficacy boundary. Abiraterone-prednisone showed superiority over prednisone alone with respect to time to initiation of cytotoxic chemotherapy, opiate use for cancer-related pain, prostate-specific antigen progression, and decline in performance status. Grade 3 or 4 mineralocorticoid-related adverse events and abnormalities on liver-function testing were more common with abiraterone-prednisone. CONCLUSIONS Abiraterone improved radiographic progression-free survival, showed a trend toward improved overall survival, and significantly delayed clinical decline and initiation of chemotherapy in patients with metastatic castration-resistant prostate cancer. (Funded by Janssen Research and Development, formerly Cougar Biotechnology; ClinicalTrials.gov number, NCT00887198.).

Enzalutamide in metastatic prostate cancer before chemotherapy

BACKGROUND Enzalutamide is an oral androgen-receptor inhibitor that prolongs survival in men with metastatic castration-resistant prostate cancer in whom the disease has progressed after chemotherapy. New treatment options are needed for patients with metastatic prostate cancer who have not received chemotherapy, in whom the disease has progressed despite androgen-deprivation therapy. METHODS In this double-blind, phase 3 study, we randomly assigned 1717 patients to receive either enzalutamide (at a dose of 160 mg) or placebo once daily. The coprimary end points were radiographic progression-free survival and overall survival. RESULTS The study was stopped after a planned interim analysis, conducted when 540 deaths had been reported, showed a benefit of the active treatment. The rate of radiographic progression-free survival at 12 months was 65% among patients treated with enzalutamide, as compared with 14% among patients receiving placebo (81% risk reduction; hazard ratio in the enzalutamide group, 0.19; 95% confidence interval [CI], 0.15 to 0.23; P<0.001). A total of 626 patients (72%) in the enzalutamide group, as compared with 532 patients (63%) in the placebo group, were alive at the data-cutoff date (29% reduction in the risk of death; hazard ratio, 0.71; 95% CI, 0.60 to 0.84; P<0.001). The benefit of enzalutamide was shown with respect to all secondary end points, including the time until the initiation of cytotoxic chemotherapy (hazard ratio, 0.35), the time until the first skeletal-related event (hazard ratio, 0.72), a complete or partial soft-tissue response (59% vs. 5%), the time until prostate-specific antigen (PSA) progression (hazard ratio, 0.17), and a rate of decline of at least 50% in PSA (78% vs. 3%) (P<0.001 for all comparisons). Fatigue and hypertension were the most common clinically relevant adverse events associated with enzalutamide treatment. CONCLUSIONS Enzalutamide significantly decreased the risk of radiographic progression and death and delayed the initiation of chemotherapy in men with metastatic prostate cancer. (Funded by Medivation and Astellas Pharma; PREVAIL ClinicalTrials.gov number, NCT01212991.).

Abiraterone acetate for treatment of metastatic castration-resistant prostate cancer: final overall survival analysis of the COU-AA-301 randomised, double-blind, placebo-controlled phase 3 study

BACKGROUND Abiraterone acetate improved overall survival in metastatic castration-resistant prostate cancer at a preplanned interim analysis of the COU-AA-301 double-blind, placebo-controlled phase 3 study. Here, we present the final analysis of the study before crossover from placebo to abiraterone acetate (after 775 of the prespecified 797 death events). METHODS Between May 8, 2008, and July 28, 2009, this study enrolled 1195 patients at 147 sites in 13 countries. Patients were eligible if they had metastatic castration-resistant prostate cancer progressing after docetaxel. Patients were stratified according to baseline Eastern Cooperative Oncology Group (ECOG) performance status, worst pain over the past 24 h on the Brief Pain Inventory-Short Form, number of previous chemotherapy regimens, and type of progression. Patients were randomly assigned (ratio 2:1) to receive either abiraterone acetate (1000 mg, once daily and orally) plus prednisone (5 mg, orally twice daily) or placebo plus prednisone with a permuted block method via an interactive web response system. The primary endpoint was overall survival, analysed in the intention-to-treat population. This study is registered with ClinicalTrials.gov, number NCT00091442. FINDINGS Of the 1195 eligible patients, 797 were randomly assigned to receive abiraterone acetate plus prednisone (abiraterone group) and 398 to receive placebo plus prednisone (placebo group). At median follow-up of 20·2 months (IQR 18·4-22·1), median overall survival for the abiraterone group was longer than in the placebo group (15·8 months [95% CI 14·8-17·0] vs 11·2 months [10·4-13·1]; hazard ratio [HR] 0·74, 95% CI 0·64-0·86; p<0·0001). Median time to PSA progression (8·5 months, 95% CI 8·3-11·1, in the abiraterone group vs 6·6 months, 5·6-8·3, in the placebo group; HR 0·63, 0·52-0·78; p<0·0001), median radiologic progression-free survival (5·6 months, 5·6-6·5, vs 3·6 months, 2·9-5·5; HR 0·66, 0·58-0·76; p<0·0001), and proportion of patients who had a PSA response (235 [29·5%] of 797 patients vs 22 [5·5%] of 398; p<0·0001) were all improved in the abiraterone group compared with the placebo group. The most common grade 3-4 adverse events were fatigue (72 [9%] of 791 patients in the abiraterone group vs 41 [10%] of 394 in the placebo group), anaemia (62 [8%] vs 32 [8%]), back pain (56 [7%] vs 40 [10%]), and bone pain (51 [6%] vs 31 [8%]). INTERPRETATION This final analysis confirms that abiraterone acetate significantly prolongs overall survival in patients with metastatic castration-resistant prostate cancer who have progressed after docetaxel treatment. No new safety signals were identified with increased follow-up.

Safety and efficacy of sunitinib for metastatic renal-cell carcinoma: an expanded-access trial

BACKGROUND Results from clinical trials have established sunitinib as a standard of care for first-line treatment of advanced or metastatic renal-cell carcinoma (RCC); however, many patients, particularly those with a poorer prognosis, do not meet inclusion criteria and little is known about the activity of sunitinib in these subgroups. The primary objective of this trial was to provide sunitinib on a compassionate-use basis to trial-ineligible patients with RCC from countries where regulatory approval had not been granted. METHODS Previously treated and treatment-naive patients at least 18 years of age with metastatic RCC were eligible. All patients received open-label sunitinib 50 mg orally once daily on schedule 4-2 (4 weeks on treatment, 2 weeks off). Safety was assessed regularly, tumour measurements done per local practice, and survival data collected where possible. Analyses were done in the modified intention-to-treat (ITT) population, which consisted of all patients who received at least one dose of sunitinib. This study is registered with ClinicalTrials.gov, NCT00130897. FINDINGS As of December, 2007, 4564 patients were enrolled in 52 countries. 4371 patients were included in the modified ITT population. This population included 321 (7%) patients with brain metastases, 582 (13%) with Eastern Cooperative Oncology Group (ECOG) performance status of 2 or higher, 588 (13%) non-clear-cell RCC, and 1418 (32%) aged 65 years or more. Patients received a median of five treatment cycles (range 1-25). Reasons for discontinuation included lack of efficacy (n=1168 [27%]) and adverse events (n=362 [8%]). The most common treatment-related adverse events were diarrhoea (n=1936 [44%]) and fatigue (n=1606 [37%]). The most common grade 3-4 adverse events were fatigue (n=344 [8%]) and thrombocytopenia (n=338 [8%]) with incidences of grade 3-4 adverse events similar across subgroups. In 3464 evaluable patients, the objective response rate (ORR) was 17% (n=603), with subgroup ORR as follows: brain metastases (26 of 213 [12%]), ECOG performance status 2 or higher (29 of 319 [9%]), non-clear-cell RCC (48 of 437 [11%]) and age 65 years or more (176 of 1056 [17%]). Median progression-free survival was 10.9 months (95% CI 10.3-11.2) and overall survival was 18.4 months (17.4-19.2). INTERPRETATION In a broad population of patients with metastatic RCC, the safety profile of sunitinib 50 mg once-daily (initial dose) on schedule 4-2 was manageable and efficacy results were encouraging, particularly in subgroups associated with poor prognosis who are not usually entered into clinical trials. FUNDING Pfizer Inc.

Cabozantinib versus Everolimus in Advanced Renal-Cell Carcinoma

BACKGROUND Cabozantinib is an oral, small-molecule tyrosine kinase inhibitor that targets vascular endothelial growth factor receptor (VEGFR) as well as MET and AXL, each of which has been implicated in the pathobiology of metastatic renal-cell carcinoma or in the development of resistance to antiangiogenic drugs. This randomized, open-label, phase 3 trial evaluated the efficacy of cabozantinib, as compared with everolimus, in patients with renal-cell carcinoma that had progressed after VEGFR-targeted therapy. METHODS We randomly assigned 658 patients to receive cabozantinib at a dose of 60 mg daily or everolimus at a dose of 10 mg daily. The primary end point was progression-free survival. Secondary efficacy end points were overall survival and objective response rate. RESULTS Median progression-free survival was 7.4 months with cabozantinib and 3.8 months with everolimus. The rate of progression or death was 42% lower with cabozantinib than with everolimus (hazard ratio, 0.58; 95% confidence interval [CI] 0.45 to 0.75; P<0.001). The objective response rate was 21% with cabozantinib and 5% with everolimus (P<0.001). A planned interim analysis showed that overall survival was longer with cabozantinib than with everolimus (hazard ratio for death, 0.67; 95% CI, 0.51 to 0.89; P=0.005) but did not cross the significance boundary for the interim analysis. Adverse events were managed with dose reductions; doses were reduced in 60% of the patients who received cabozantinib and in 25% of those who received everolimus. Discontinuation of study treatment owing to adverse events occurred in 9% of the patients who received cabozantinib and in 10% of those who received everolimus. CONCLUSIONS Progression-free survival was longer with cabozantinib than with everolimus among patients with renal-cell carcinoma that had progressed after VEGFR-targeted therapy. (Funded by Exelixis; METEOR ClinicalTrials.gov number, NCT01865747.).

Cabozantinib versus everolimus in advanced renal cell carcinoma (METEOR): final results from a randomised, open-label, phase 3 trial

BACKGROUND Cabozantinib is an oral inhibitor of tyrosine kinases including MET, VEGFR, and AXL. The randomised phase 3 METEOR trial compared the efficacy and safety of cabozantinib versus the mTOR inhibitor everolimus in patients with advanced renal cell carcinoma who progressed after previous VEGFR tyrosine-kinase inhibitor treatment. Here, we report the final overall survival results from this study based on an unplanned second interim analysis. METHODS In this open-label, randomised phase 3 trial, we randomly assigned (1:1) patients aged 18 years and older with advanced or metastatic clear-cell renal cell carcinoma, measurable disease, and previous treatment with one or more VEGFR tyrosine-kinase inhibitors to receive 60 mg cabozantinib once a day or 10 mg everolimus once a day. Randomisation was done with an interactive voice and web response system. Stratification factors were Memorial Sloan Kettering Cancer Center risk group and the number of previous treatments with VEGFR tyrosine-kinase inhibitors. The primary endpoint was progression-free survival as assessed by an independent radiology review committee in the first 375 randomly assigned patients and has been previously reported. Secondary endpoints were overall survival and objective response in all randomly assigned patients assessed by intention-to-treat. Safety was assessed per protocol in all patients who received at least one dose of study drug. The study is closed for enrolment but treatment and follow-up of patients is ongoing for long-term safety evaluation. This trial is registered with ClinicalTrials.gov, number NCT01865747. FINDINGS Between Aug 8, 2013, and Nov 24, 2014, 658 patients were randomly assigned to receive cabozantinib (n=330) or everolimus (n=328). The median duration of follow-up for overall survival and safety was 18·7 months (IQR 16·1-21·1) in the cabozantinib group and 18·8 months (16·0-21·2) in the everolimus group. Median overall survival was 21·4 months (95% CI 18·7-not estimable) with cabozantinib and 16·5 months (14·7-18·8) with everolimus (hazard ratio [HR] 0·66 [95% CI 0·53-0·83]; p=0·00026). Cabozantinib treatment also resulted in improved progression-free survival (HR 0·51 [95% CI 0·41-0·62]; p<0·0001) and objective response (17% [13-22] with cabozantinib vs 3% [2-6] with everolimus; p<0·0001) per independent radiology review among all randomised patients. The most common grade 3 or 4 adverse events were hypertension (49 [15%] in the cabozantinib group vs 12 [4%] in the everolimus group), diarrhoea (43 [13%] vs 7 [2%]), fatigue (36 [11%] vs 24 [7%]), palmar-plantar erythrodysaesthesia syndrome (27 [8%] vs 3 [1%]), anaemia (19 [6%] vs 53 [17%]), hyperglycaemia (3 [1%] vs 16 [5%]), and hypomagnesaemia (16 [5%] vs none). Serious adverse events grade 3 or worse occurred in 130 (39%) patients in the cabozantinib group and in 129 (40%) in the everolimus group. One treatment-related death occurred in the cabozantinib group (death; not otherwise specified) and two occurred in the everolimus group (one aspergillus infection and one pneumonia aspiration). INTERPRETATION Treatment with cabozantinib increased overall survival, delayed disease progression, and improved the objective response compared with everolimus. Based on these results, cabozantinib should be considered as a new standard-of-care treatment option for previously treated patients with advanced renal cell carcinoma. Patients should be monitored for adverse events that might require dose modifications. FUNDING Exelixis Inc.

Effect of abiraterone acetate and prednisone compared with placebo and prednisone on pain control and skeletal-related events in patients with metastatic castration-resistant prostate cancer: exploratory analysis of data from the COU-AA-301 randomised trial.

BACKGROUND Bone metastases are a major cause of morbidity in metastatic castration-resistant prostate cancer. Abiraterone acetate potently disrupts intracrine androgen receptor signalling pathways implicated in the progression of the disease, including bone metastases. We assessed data for pain control and skeletal-related events prospectively collected as part of the randomised, phase 3 COU-AA-301 trial of abiraterone acetate plus prednisone versus placebo plus prednisone in patients with metastatic castration-resistant prostate cancer after docetaxel chemotherapy. METHODS The COU-AA-301 trial enrolled patients with metastatic castration-resistant prostate cancer in whom one or two lines of chemotherapy (one docetaxel based) had been unsuccessful and who had Eastern Cooperative Oncology Group performance statuses of 2 or less. Pain intensity and interference of pain with daily activities were assessed with the Brief Pain Inventory-Short Form questionnaire at baseline, day 15 of cycle 1, and day 1 of each treatment cycle thereafter until discontinuation. We assessed, with prospectively defined response criteria that incorporated analgesic use, clinically meaningful changes in pain intensity and interference with daily living. We measured time to first occurrence of skeletal-related events, which we defined as pathological fracture, spinal cord compression, palliative radiation to bone, or bone surgery, and regularly assessed them throughout the study. Pain palliation was assessed in patients who had clinically significant baseline pain, whereas all other analyses were done in the overall intention-to-treat population. COU-AA-301 is registered with ClinicalTrials.gov, number NCT00638690. FINDINGS Median follow-up was 20·2 months (IQR 18·4-22·1). In patients with clinically significant pain at baseline, abiraterone acetate and prednisone resulted in significantly more palliation (157 of 349 [45·0%] patients vs 47 of 163 [28·8%]; p=0·0005) and faster palliation (median time to palliation 5·6 months [95% CI 3·7-9·2] vs 13·7 months [5·4-not estimable]; p=0·0018) of pain intensity than did prednisone only. Palliation of pain interference (134 of 223 [60·1%] vs 38 of 100 [38·0%], p=0·0002; median time to palliation of pain interference 1·0 months [95% CI 0·9-1·9] vs 3·7 months [2·7-not estimable], p=0·0004) and median duration of palliation of pain intensity (4·2 months [95% CI 3·0-4·9] vs 2·1 months [1·4-3·7]; p=0·0056) were significantly better with abiraterone acetate and prednisone than with prednisone only. In the overall population, median time to occurrence of first skeletal-related event was significantly longer with abiraterone acetate and prednisone than with prednisone only (25·0 months [95% CI 25·0-not estimable] vs 20·3 months [16·9-not estimable]; p=0·0001). INTERPRETATION In patients with metastatic castration-resistant prostate cancer previously treated with docetaxel, abiraterone acetate and prednisone offer significant benefits compared with prednisone alone in terms of pain relief, delayed pain progression, and prevention of skeletal-related events. FUNDING Janssen Research & Development and Janssen Global Services.

Cediranib With mFOLFOX6 Versus Bevacizumab With mFOLFOX6 As First-Line Treatment for Patients With Advanced Colorectal Cancer: A Double-Blind, Randomized Phase III Study (HORIZON III)

PURPOSE To compare the efficacy of cediranib (a vascular endothelial growth factor receptor tyrosine kinase inhibitor [VEGFR TKI]) with that of bevacizumab (anti-VEGF-A monoclonal antibody) in combination with chemotherapy as first-line treatment for advanced metastatic colorectal cancer (mCRC). PATIENTS AND METHODS HORIZON III [Cediranib Plus FOLFOX6 Versus Bevacizumab Plus FOLFOX6 in Patients With Untreated Metastatic Colorectal Cancer] had an adaptive phase II/III design. Patients randomly assigned 1:1:1 received mFOLFOX6 [oxaliplatin 85 mg/m(2) and leucovorin 400 mg/m(2) intravenously followed by fluorouracil 400 mg/m(2) intravenously on day 1 and then continuous infusion of 2,400 mg/m(2) over the next 46 hours every 2 weeks] with cediranib (20 or 30 mg per day) or bevacizumab (5 mg/kg every 14 days). An independent end-of-phase II analysis concluded that mFOLFOX6/cediranib 20 mg met predefined criteria for continuation; subsequent patients received mFOLFOX6/cediranib 20 mg or mFOLFOX6/bevacizumab (randomly assigned 1:1). The primary objective was to compare progression-free survival (PFS). RESULTS In all, 1,422 patients received mFOLFOX6/cediranib 20 mg (n = 709) or mFOLFOX6/bevacizumab (n = 713). Primary analysis revealed no significant difference between arms for PFS (hazard ratio [HR], 1.10; 95% CI, 0.97 to 1.25; P = .119), overall survival (OS; HR, 0.95; 95% CI, 0.82 to 1.10; P = .541), or overall response rate (46.3% v 47.3%). Median PFS and OS were 9.9 and 22.8 months for mFOLFOX6/cediranib and 10.3 and 21.3 months for mFOLFOX6/bevacizumab. The PFS upper 95% CI was outside the predefined noninferiority limit (HR < 1.2). Common adverse events with more than 5% incidence in the cediranib arm included diarrhea, neutropenia, and hypertension. Cediranib-treated patients completed fewer chemotherapy cycles than bevacizumab-treated patients (median 10 v 12 cycles). Patient-reported outcomes (PROs) were significantly less favorable in cediranib-treated versus bevacizumab-treated patients (P < .001). CONCLUSION Cediranib activity, in terms of PFS and OS, was comparable to that of bevacizumab when added to mFOLFOX6; however, the predefined boundary for PFS noninferiority was not met. The cediranib safety profile was consistent with previous studies but led to less favorable PROs compared with bevacizumab. Investigation of oral TKIs in CRC continues.

Abiraterone acetate plus prednisone versus prednisone alone in chemotherapy-naive men with metastatic castration-resistant prostate cancer: patient-reported outcome results of a randomised phase 3 trial

BACKGROUND Abiraterone acetate plus prednisone significantly improves radiographic progression-free survival in asymptomatic or mildly symptomatic, chemotherapy-naive patients with metastatic castration-resistant prostate cancer compared with prednisone alone. We describe analyses of data for patient-reported pain and functional status in a preplanned interim analysis of a phase 3 trial. METHODS Between April 28, 2009, and June 23, 2010, patients with progressive, metastatic castration-resistant prostate cancer were enrolled into a multinational, double-blind, placebo-controlled trial. Patients were eligible if they were asymptomatic (score of 0 or 1 on item three of the Brief Pain Inventory Short Form [BPI-SF] questionnaire) or mildly symptomatic (score of 2 or 3) and had not previously received chemotherapy. Patients were randomly assigned (1:1) to receive oral abiraterone (1 g daily) plus prednisone (5 mg twice daily) or placebo plus prednisone in continuous 4-week cycles. Pain was assessed with the BPI-SF questionnaire, and health-related quality of life (HRQoL) with the Functional Assessment of Cancer Therapy-Prostate (FACT-P) questionnaire. We analysed data with prespecified criteria for clinically meaningful pain progression and deterioration in HRQoL. All patients who underwent randomisation were included in analyses. FINDINGS 1088 patients underwent randomisation: 546 were assigned to abiraterone plus prednisone and 542 to placebo plus prednisone. At the time of the second prespecified interim analysis, median follow-up was 22·2 months (IQR 20·2-24·8). Median time to progression of mean pain intensity was longer in patients assigned to abiraterone plus prednisone (26·7 months [95% CI 19·3-not estimable]) than in those assigned to placebo plus prednisone (18·4 months [14·9-not estimable]; hazard ratio [HR] 0·82, 95% CI 0·67-1·00; p=0·0490), as was median time to progression of pain interference with daily activities (10·3 months [95% CI 9·3-13·0] vs 7·4 months [6·4-8·6]; HR 0·79, 95% CI 0·67-0·93; p=0·005). Median time to progression of worst pain was also longer with abiraterone plus prednisone (26·7 months [95% CI 19·4-not estimable]) than with placebo plus prednisone (19·4 months [16·6-not estimable]), but the difference was not significant (HR 0·85, 95% CI 0·69-1·04; p=0·109). Median time to HRQoL deterioration was longer in patients assigned to abiraterone plus prednisone than in those assigned to placebo plus prednisone as assessed by the FACT-P total score (12·7 months [95% CI 11·1-14·0] vs 8·3 months [7·4-10·6]; HR 0·78, 95% CI 0·66-0·92; p=0·003) and by the score on its prostate-cancer-specific subscale (11·1 months [8·6-13·8] vs 5·8 months [5·5-8·3]; HR 0·70, 95% CI 0·60-0·83; p<0·0001). INTERPRETATION Abiraterone plus prednisone delays patient-reported pain progression and HRQoL deterioration in chemotherapy-naive patients with metastatic castration-resistant prostate cancer. These results provide further support for the efficacy of abiraterone in this population.