Factors influencing early therapy discontinuation in men with metastatic, castration-resistant prostate carcinoma treated with abiraterone acetate plus prednisone: a real-world prospective cohort study (IMPACT)

Introduction and objective: Abiraterone acetate plus prednisone (AA+P) has been proven effective in randomized controlled trials and real-world studies in men with metastatic, castration-resistant prostate carcinoma (mCRPC). Treatment duration is an indicator of success of oral prostate cancer therapy. The objective of this prospective cohort study was to assess factors that may impact time to treatment discontinuation in men with mCRPC treated with AA+P prior to or following chemotherapy.

Methods: This was a prospective cohort study performed under real-world conditions in Germany. We performed a multivariate Cox proportional hazard regression analysis to assess the influence of baseline characteristics on time to treatment discontinuation.  

Results: In the final analysis, 675 patients were included. With regards to baseline characteristics the mean age was 74.7 years (+/- 7.7 standard deviation). 203 patients (30.1%) received prior chemotherapy. The mean PSA was 191.1 ng/ml (+/- 479.2 standard deviation) and  523 patients (77.5%) had a high adherence according to Morisky medication adherence scale-4.. The median duration of treatment with AA+P was 10.2 months in the total population, 11.4 months in pre-chemotherapy patients and 7.6 months in post-chemotherapy patients. Table 2 shows the results of the multivariate regression for the risk of early discontinuation.

Table 2

Conclusion: In this prospective cohort, treatment duration under real world conditions for pre- and post-chemotherapy was similar to the respective registrational trials (COU-AA-302 and 301), and higher than in previously published retrospective analyses. Post-chemotherapy patients, older patients and patients with low/medium baseline adherence appear to be at a higher risk for early treatment discontinuation.