Abstract 648P
Background
Abiraterone acetate (AA) combined with prednisone (P) is a major treatment for metastatic castration-resistant prostate cancer (mCRPC). In case of resistance to AA+P other drugs such as docetaxel and enzalutamide can be used. The combination of AA and dexamethasone (D) has been described as another possible option, immediately (switch) or in rechallenge after a different treatment line.
Methods
77 patients with mCRPC were included in this retrospective study conducted in two centers. All patients received AA + P. After disease progression on AA+P, patients were treated either first with another drug and then rechallenge of AA combined with D or with an immediate switch from P to D. Progression was defined by PCWG3 criteria. The efficacy of AA+D was estimated by the proportion of patients with a PSA decline > 50% from baseline value (PSA50), a PSA decline > 30% from baseline value (PSA30) and progression-free survival (PFS).
Results
Median duration of treatment with AA + D was 533 days. 22/77 (28.6%) patients had a PSA50 (90% CI: 20.2-38.2) and 28/77 (36.3%) PSA30 (90% CI: 27-46). The biological response rate was no different whether the patients were treated in a switch or rechallenge context. Patients with prior response on AA + P were more likely to achieve PSA50 on AA + D, but the results were not significant: 17/77 (34.6%) versus 4/77 (16%, p = 0.09). Age was found as a predictive factor for PSA50: OR 0.93 (CI 97.5%: 0.87-0.99; p < 0.05). Median PFS on AA+D was 4.2 months. PFS was similar after either switch or rechallenge. Treatment with AA+D was well tolerated, with no significant mineralocorticoid syndrome and no grade ≥3 adverse events.
Conclusions
Directly switch from P to D after progression or AA+D rechallenge may be an effective treatment in men without clinical deterioration. Data on predictive factors of response will be further presented.
Clinical trial identification
Editorial acknowledgement
Legal entity responsible for the study
The authors.
Funding
Has not received any funding.
Disclosure
G. Baciarello: Honoraria (self): Janssen; Honoraria (self): Roche; Honoraria (institution): Amgen; Honoraria (institution): Astellas Oncology; Honoraria (institution): Janssen; Honoraria (institution): Roche; Travel/Accommodation/Expenses: Astellas Oncology; Travel/Accommodation/Expenses: Ipsen; Travel/Accommodation/Expenses: Janssen; Travel/Accommodation/Expenses: Roche. C. Dumont: Travel/Accommodation/Expenses: Ipsen. K. Fizazi: Honoraria (self): Astellas Pharma; Honoraria (self): Janssen; Honoraria (self): Merck; Honoraria (self): Sanofi; Advisory/Consultancy: Amgen; Advisory/Consultancy: Astellas Pharma; Advisory/Consultancy: AstraZeneca; Advisory/Consultancy: Bayer; Advisory/Consultancy: Clovis Oncology; Advisory/Consultancy: CureVac; Advisory/Consultancy: ESSA Pharma; Advisory/Consultancy: Janssen Oncology; Advisory/Consultancy: Orion Pharma GmbH; Advisory/Consultancy: Roche/Genentech; Advisory/Consultancy: Sanofi; Travel/Accommodation/Expenses: Amgen; Travel/Accommodation/Expenses: Janssen. S. Culine: Advisory/Consultancy: Astellas Oncology; Advisory/Consultancy: Bayer; Advisory/Consultancy: Janssen; Advisory/Consultancy: Roche; Travel/Accommodation/Expenses: Janssen; Travel/Accommodation/Expenses: MSD Oncology; Travel/Accommodation/Expenses: Roche. All other authors have declared no conflicts of interest.