ASCO 2018: Abi Race: A Prospective, Multicenter Study of Black and White Patients with Metastatic Castrate Resistant Prostate Cancer Treated with Abiraterone Acetate and Prednisone

Chicago, IL (UroToday.com) Black men have 2.5 times greater likelihood of dying from prostate cancer but have been under represented in phase 3 trials. [1] Black men have been demonstrated to have longer radiographical progression free survival (RPFS) when treated with abiraterone, compared to the overall population, in the COU- 302 trial. [2] To support the hypothesis that black men have a greater PSA response rate than white men to abiraterone, the authors performed a multicenter prospective parallel group study of abiraterone in men with metastatic castrate resistant prostate cancer (mCRPC) to evaluate outcome by race (NCT01940276).

The primary endpoint of this study was RPFS by race. Secondary endpoints included confirmed PSA response rates of >=30%, >=50%, >=90% declines, as well as PSA progression free survival (PSA PFS). Additional outcomes included safety and tolerability by race. All included patients were MCRPC with castrated testosterone levels, and PSA >= 2 ng/ ml. Exclusion criteria included: patients who received chemotherapy prior to transitioning to CRPC, had uncontrolled hypertension, received prior abiraterone or enzalutamide therapy, had poorly controlled diabetes, and any significant cardiovascular event in the last 6 months prior to study enrollment. The trial schema is shown in figure 1.
image 6Figure 1 – Trial schema
Overall the baseline characteristics of all accrued patients were similar. In total 50 black and 50 white patients were analyzed. The results demonstrated that the median RPFS for black patients and white patients was 16.7 months and 16.5 months, respectively. However, the PSA PFS was different among black and white patients, with a median PSA PFS of 16.6 and 11.5 months in black and white patients, respectively. Black patients were shown to have higher rates of ≥30%, ≥50% and ≥90% PSA decline [Figure 2].

image 6bFigure 2 – Result

When assessing the adverse events, it was clearly seen that constipation, hyperglycemia, hypokalemia, insomnia, and hot flashes were higher in the black patients. In contrast, vomiting, fatigue headaches, cough and weight gain were higher tin the white patients.

This is the first prospective multicenter study comparing MCRPC patients of different race, demonstrating the feasibility of conducting studies inclusive of black men with MCRPC.

The authors concluded that black men with MCRPC have greater and more durable PSA responses to abiraterone than white men. However, no radiographical response rate difference was seen among the two populations. Interestingly, adverse events evidently vary by race, with black patients experiencing different adverse events than white patients. According to the results of this trial, the effect of abiraterone in hormone sensitive settings must also be evaluated in populations by race.

Presented by: Daniel J. George, Duke University, Durham, NC

Written by: Hanan Goldberg, MD, Urologic Oncology Fellow (SUO), University of Toronto, Princess Margaret Cancer Centre, Twitter:@GoldbergHanan at the 2018 ASCO Annual Meeting - June 1-5, 2018 – Chicago, IL USA

References:
[1] SEER stat fact sheets: Prostate. Available from http:/SEER.cancer.gov/statfacts/html/prost.html
[2] Ryan CJ, et al. N eng J med 2013;368:138-48
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