VIENNA—Abiraterone plus prednisone, compared to placebo plus prednisone, may help delay pain progression and functional decline in patients with asymptomatic or mildly symptomatic metastatic castration-resistant prostate cancer (mCRPC) patients whose disease has progressed after androgen deprivation therapy, according to new data presented at the European Society for Medical Oncology 2012 Congress.

“We now have medications where the side effect ratio is very favorable so that the therapies don’t affect quality of life,” said principal investigator Charles J. Ryan, MD, Associate Professor of Clinical Medicine at the University of California-San Francisco Helen Diller Family Comprehensive Cancer Center. “The results were not surprising and they showed that patient not only lived longer and but had better quality of life.”

The new data were presented at the meeting by Ethan Basche, MD, of the University of North Carolina in Chapel Hill.

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The investigators evaluated the impact of abiraterone on pain and functional status as part of a large phase 3 trial that included patients with asymptomatic or mildly symptomatic, progressive, chemotherapy-naïve mCRPC. The randomized, double-blind, placebo-controlled trial included 1,088 men with mCRPC who had not received prior chemotherapy. Investigators randomized 546 subjects to receive abiraterone 1,000 mg orally once daily plus prednisone 5 mg twice daily and 542 patients to receive placebo plus prednisone 5 mg twice daily (controls). 

The co-primary endpoints of the study were radiographic progression-free survival (rPFS) and overall survival (OS). Secondary endpoints were functional status and pain progression. The patients reported their pain and functional status at baseline and on the first day of pre-specified treatment cycles over 13.8 months and 8.3 months in the two arms, respectively. Researchers performed these assessments using standard, validated instruments: the Brief Pain Inventory – Short Form (BPI-SF) and the Functional Assessment of Cancer Therapy – Prostate Cancer (FACT-P).

Dr. Ryan and his colleagues found that patients in the abiraterone arm reported statistically significant delays in most measures of pain progression and functional decline compared with  those in the control arm, and pre-defined degrees of worsening were greater (more delayed) in the abiraterone arm compared with the control arm. Baseline scores were similar between the two arms at baseline, when the median worst pain intensity score was 1.2 and the median pain interference score was 0.7 in each arm.

Abiraterone recipients had significantly delayed average pain intensity progression, pain interference progression, and degradation in FACT-P total score and all subscales except the social/family well-being subscale, where the two groups showed no statistical difference.

The mean time to pain progression was 26.7 months in the abiraterone arm compared with 18.4 months in the control group; the mean time to worst pain intensity progression was 14.8 months and 12 months, respectively. The mean time to progression of pain interference with daily function was 10.3 and 7.4 months, respectively. The median time to opiate use for cancer pain was not reached in abiraterone arm; it was 23.7 months for the control group arm.

The median FACT-G score (general function status) was 16.6 for the abiraterone recipients compared with 11.1 for controls. The median FACT-P total scores were 12.7 and 8, respectively. The physical well-being instrument revealed median scores of 14.8 and 11.1, respectively. The abiraterone group also demonstrated better emotional well-being (22.1 vs. 14.2), functional well-being (13.3 vs. 8.4 months), and prostate cancer subscale score (11.1 vs. 5.8). All of the differences in scores between the two groups were statistically significant.

The study revealed no statistically significant difference between the groups with respect to social/family well-being (18.4 vs. 16.6).

“This is a patient population that has not been significantly impaired by the disease yet, so the idea is to preserve quality of life and to try to keep them at a good level,” Dr. Ryan said.