Clinical outcomes in patients with metastatic castrate-resistant prostate cancer treated with abiraterone with or without ongoing androgen deprivation therapy: A retrospective case-control study

Abstract

Introduction: Abiraterone and concurrent androgen deprivation therapy (ADT) are used in the treatment of patients with metastatic castration-resistant prostate cancer. Recently, it has been suggested that the use of abiraterone alone (without ADT) may have comparable efficacy to abiraterone with ongoing ADT. Here, we sought to assess the impact of ADT cessation in patients beginning abiraterone for castration-resistant prostate cancer.

Methods: We identified 39 patients at our institution who received abiraterone alone (with discontinuation of ADT) between 2011 and 2022. We then procured a comparable group of 39 patients (matched by age, Gleason score, and prostate-specific antigen [PSA] level) who received abiraterone with ongoing ADT during the same period. We assessed and compared clinical outcomes in the two groups (abiraterone-alone vs. abiraterone-ADT) with respect to PSA response rates, PSA progression-free survival, and overall survival. Results were adjusted using Cox proportional-hazards multivariable models.

Results: The median PSA before treatment initiation was 12.7 (range: 0.2-199) ng/mL in the abiraterone-alone group and 15.5 (range: 0.6-212) ng/mL in the abiraterone-ADT group. Use of abiraterone alone adequately suppressed testosterone levels in 35/37 (94.6%) patients. Patients receiving abiraterone alone had a median PSA reduction of 80.2% versus 79.5% in patients receiving abiraterone plus ADT. The median PSA progression-free survival in patients receiving abiraterone alone was 27.4 versus 25.8 months in patients receiving abiraterone plus ADT (hazard ratio [HR] 1.10; 95% confidence interval [CI] 0.65-1.71; p = 0.82). In addition, abiraterone alone was associated with an overall survival of 3.6 versus 3.1 years in patients receiving abiraterone plus ADT (HR 0.90; 95% CI 0.50-1.62; p = 0.72). There were no differences in PFS or OS between groups after performing Cox multivariable regression analyses.

Conclusion: Use of abiraterone alone was associated with comparable clinical outcomes to patients who received abiraterone together with ADT. Further prospective studies are warranted to evaluate the impact of abiraterone alone on treatment outcomes and cost savings.

Keywords: ADT; abiraterone; overall survival; progression-free survival; retrospective case-control study.

Figure 1:. Waterfall plots of best PSA response.

Figure 1A shows the 39 patients treated with abiraterone only. Figure 1B shows the 39 patients treated with abiraterone and ADT. The black dotted line indicates a PSA response greater than or equal to 50% reduction in PSA level from baseline. The red dotted line indicates the median PSA reduction from the baseline. Asterisks indicate an increase of more than 100% in best PSA response.

Figure 1:. Waterfall plots of best PSA response.

Figure 1A shows the 39 patients treated with abiraterone only. Figure 1B shows the 39 patients treated with abiraterone and ADT. The black dotted line indicates a PSA response greater than or equal to 50% reduction in PSA level from baseline. The red dotted line indicates the median PSA reduction from the baseline. Asterisks indicate an increase of more than 100% in best PSA response.

Figure 2:. Kaplan-Meier plot of PSA progression-free survival.

Figure 2 shows the PSA-based progression-free survival among the 78 patients who received abiraterone alone or abiraterone and ADT.

Figure 3:. Kaplan-Meier plot of overall survival.

Figure 3 shows the overall survival among the 78 patients who received abiraterone alone or abiraterone and ADT.