Survival by race in men with chemotherapy-naive enzalutamide- or abiraterone-treated metastatic castration-resistant prostate cancer

Abstract

Background Black men are more likely to be diagnosed with aggressive prostate cancer (PC) and die from PC than white men. However, black men with metastatic castration-resistant PC (mCRPC) had longer overall survival (OS) than white men when treated with certain agents in clinical trials. We analyzed claims data from the Veterans Health Administration (VHA) database to evaluate OS in black and white men treated with enzalutamide or abiraterone (novel hormonal therapy [NHT]) for chemotherapy-naïve mCRPC. Methods Patients with mCRPC aged ≥18 years were identified in the VHA database by diagnosis codes, evidence of surgical/medical castration, and a prescription claim for enzalutamide or abiraterone after castration from April 2014–March 2017. Cox models assessed associations between race and OS. Unadjusted and multivariable analyses were performed on the entire population and subsets based on the type of therapy received (if any) after NHT. Results In total, 2910 patients were identified (787 black, mean 71.7 years; 2123 white, mean 74.0 years). Median follow-up was 19.0 and 18.7 months in blacks and whites, respectively. Black men had better survival versus white men: hazard ratios (95% CIs) were 0.89 (0.790–0.996; P = 0.044) and 0.67 (0.592–0.758; P < 0.0001) in the unadjusted and multivariable models, respectively. Statistically significantly longer OS was seen in black versus white men regardless of subsequent treatment, including no subsequent treatment. Conclusions In the VHA, black men with chemotherapy-naïve mCRPC initiating NHT may have better outcomes than similarly treated white men.

Prostate-specific antigen response and clinical progression-free survival in Black and White men with chemotherapy-naïve metastatic castration-resistant prostate cancer treated with enzalutamide in a real-world setting

“…A few studies have shown that Black men tend to have a more significant PSA response (≥50% PSA level decline) than White men when treated with NHTs [20,21]. In this study, Black men with chemotherapy-naïve PC had improved clinical survival outcomes (cPFS) compared with White men, a result that is consistent with previous evidence showing that Black men with mCRPC have a reduced risk of progression and better OS when treated with NHTs and other life-prolonging therapies [20,26,27]. These prior studies on NHTs combined data from enzalutamide plus abiraterone or analyzed abiraterone alone, unlike the current study, which focused only on enzalutamide and addressed the limited amount of real-world PSA response literature for enzalutamide treatment.…”

“…A growing body of evidence suggests the clinical benefit of enzalutamide for the treatment of advanced PC in Black and White men [20,21,26]. A few studies have shown that Black men tend to have a more significant PSA response (≥50% PSA level decline) than White men when treated with NHTs [20,21].…”

“…Our study evaluated cPFS, a more conservative endpoint than PSA-PFS, which focuses only on the increase in PSA. cPFS as a composite endpoint has been used previously as one of the endpoints to assess the efficacy of enzalutamide in patients with metastatic PC [28] Another study, which had a median follow-up of 19 months, showed that Black men with mCRPC had a significantly lower risk of death than White men, with a 33% risk reduction when treated with NHTs (either abiraterone or enzalutamide as first-line therapy) [26]. Conversely, a recent study using the community oncology EHR Flatiron Health database with a short median follow-up duration (13 months) showed that although treatment with both NHTs was associated with a similar median OS in White men and Black men (24 months), enzalutamide may have a marked superiority over abiraterone in increasing OS in White men (median OS: 20 months [enzalutamide] vs. 17 months [abiraterone]; HR of death 1.21; 95% CI 1.06-1.38) [27].…”

“…Conversely, a recent study using the community oncology EHR Flatiron Health database with a short median follow-up duration (13 months) showed that although treatment with both NHTs was associated with a similar median OS in White men and Black men (24 months), enzalutamide may have a marked superiority over abiraterone in increasing OS in White men (median OS: 20 months [enzalutamide] vs. 17 months [abiraterone]; HR of death 1.21; 95% CI 1.06-1.38) [27]. The difference in outcomes observed in the latter two studies may be attributable to the inherent strengths and limitations of the study designs and the analyzed data source [26,27]. Further, the 12month landmark cPFS analysis was performed in this study to assess early trends in treatment outcome and to address the challenge of non-availability of data for the entire follow-up period due to movement of patients to an oncology setting.…”

Do disease status and race affect the efficacy of zoledronic acid in patients with prostate cancer? A systematic review and meta-analysis of randomized control trials

“…However, an increasing number of studies have valued race in cancer treatment. A study evaluated survival by race in men with chemotherapy-naive enzalutamide- or abiraterone-treated mCRPC and suggested that black men may have better outcomes than white men [ 37 ]. In line with this, another study reported that black men had a statistically significant increase in OS compared to white men [ 38 ].…”