Abiraterone acetate plus prednisone (AAP) and apalutamide may improve outcomes, compared with bicalutamide, in a subgroup of patients with prostate cancer receiving androgen deprivation therapy (ADT) and salvage radiation after radical prostatectomy, according to researchers.
The researchers found that, in the overall cohort of the FORMULA-509 trial, AAP plus apalutamide did not provide a significant improvement in progression-free survival (PFS) or metastasis-free survival (MFS).
However, AAP plus apalutamide did provide a significant improvement in PFS and MFS for patients with prostate-specific antigen (PSA) levels greater than 0.5 ng/mL.
These results were presented at the 2023 ASCO Genitourinary Cancers Symposium by Paul L. Nguyen, MD, of the Dana-Farber Cancer Institute and Harvard Medical School in Boston, Massachusetts.
The FORMULA-509 trial (ClinicalTrials.gov Identifier: NCT03141671) enrolled 345 patients with a PSA level greater than 0.1 ng/mL after radical prostatectomy and at least 1 unfavorable risk factor. The median age at baseline was 64.7 years, patients had a median PSA of 0.3 ng/mL, 35.1% had a Gleason score of 9, and 28.7% had pN1 disease.
All patients received salvage radiation and 6 months of ADT with a gonadotropin-releasing hormone agonist. They were also randomly assigned to receive bicalutamide (n=172) or AAP and apalutamide (n=173).
At a median follow-up of 34 months, the 3-year PFS rate was 74.9% in the AAP-apalutamide arm and 68.5% in the bicalutamide arm (hazard ratio [HR], 0.71; 90% CI, 0.49-1.03; P =.06). The 3-year MFS rate was 90.6% and 87.2%, respectively (HR, 0.57; 90% CI, 0.33-1.01; P =.05).
Among patients with a PSA greater than 0.5 ng/mL, the 3-year PFS and MFS rates were significantly higher with AAP-apalutamide than with bicalutamide. The 3-year PFS rate was 67.2% and 46.8%, respectively (HR, 0.50; 95% CI, 0.27-0.95; P =.03). The 3-year MFS rate was 84.3% and 66.1%, respectively (HR, 0.32; 95% CI, 0.13-0.84; P =.02).
Grade 2 or higher toxicities that were more common in the AAP-apalutamide arm than in the bicalutamide arm were hypertension (21.8% vs 13.3%), maculopapular rash (11.5% vs 0.6%), diarrhea (8.5% vs 4.8%), and fatigue (7.9% vs 6.1%). Grade 2 or higher cardiac disorders were more common with bicalutamide than with AAP-apalutamide (5.5% vs 3.0%).
“[A]lthough this primary analysis … did not meet the prespecified threshold for statistical significance, it does strongly suggest that the addition of abiraterone and apalutamide to salvage radiation and 6 months of ADT may improve progression-free survival and metastasis-free survival, particularly in the subgroup of patients with a PSA greater than 0.5,” Dr Nguyen said.
Disclosures: This research was supported by Janssen Oncology. Some study authors declared affiliations with biotech, pharmaceutical, and/or device companies. Please see the original reference for a full list of disclosures.
Nguyen PL, Kollmeier M, Rathkopf DE, et al. FORMULA-509: A multicenter randomized trial of post-operative salvage radiotherapy (SRT) and 6 months of GnRH agonist with or without abiraterone acetate/prednisone (AAP) and apalutamide (Apa) post-radical prostatectomy (RP). ASCO GU 2023. February 16-18, 2023. Abstract 303.