(UroToday.com) The 2024 ESMO annual meeting included a session on prostate cancer, featuring a presentation by Dr. Vincenza Conteduca discussing results from RAPSON, an open-label multicenter randomized trial of Radium-223 -> docetaxel versus docetaxel -> Radium-223 sequence in mCRPC with prospective biomarker evaluation. Defining the most effective treatment sequence between the α emitter Radium-223 and docetaxel is pivotal for optimizing bone-dominant mCRPC outcomes.
RAPSON is a prospective, multicenter, randomized phase 2 trial in 70 patients with symptomatic bone-dominant mCRPC who progressed after ADT ± abiraterone or enzalutamide. Patients were initially randomized 1:1 to receive Radium-223 or docetaxel as first treatment followed by docetaxel or Radium-223, respectively, at progression. The primary endpoint was the impact of sequential therapy on the percentage of patients with symptomatic bone-dominant mCRPC experiencing changes in health-related quality of life measured with the Functional Assessment of Cancer Therapy Prostate (FACT-P) questionnaire from baseline to week 12. The trial design for RAPSON is as follows:
The upper limit of the minimally important difference range was used to evaluate these changes. Patients experiencing a quality of life increase ≥ minimally important difference of FACT-P questionnaire were considered responders, whereas patients experiencing a decrease in quality of life score ≥ minimally important difference were considered no responders. The schedule for PRO assessment is highlighted below:
At a median follow-up of 13 months (range 4-45), a preliminary responder analysis at week 12 showed 33% versus 50% of patients experiencing a worsening of FACT-P questionnaire score (22% versus 50% in the physical well-being subscale) in Radium-223 versus docetaxel arm, respectively. The mean change in FACT-P total scores from baseline to week 12 was 4 (SD 16.84) for Radium-223 and 7.87 (SD 14.08) for docetaxel, with a difference between groups of 3.87 (95% CI -9.14 to 16.89):
On the BPI-SF questionnaire, a responder analysis showed a higher incidence of responders in terms of pain intensity and its interference with daily activities in the Radium-223 versus docetaxel arm:
Radium-223 -> docetaxel resulted in an improvement of quality of life compared to docetaxel -> Radium-223, also in terms of better tolerability (2 versus 7 discontinuations, and 1 versus 9 dose reductions related to Radium-223 vs docetaxel, respectively):
Efficacy results reported no difference in progression-free survival and overall survival between Radium-223 and docetaxel evaluated only for step 1 as only 14 patients completed step 2 so far:
Dr. Conteduca concluded her presentation discussing results from the RAPSON trial with the following take-home points:
- RAPSON trial provided evidence to support the use of Radium-223 prior to chemotherapy in bone-dominant symptomatic mCRPC with a clinical benefit in terms of better quality of life and tolerability
- No treatment differences in progression-free survival and overall survival were observed between the two treatment sequence arms.
- Additional follow-up and ongoing identification of outcome predictors may allow a more personalized approach to this sequential therapy strategy.
Presented by: Vincenza Conteduca, MD, Associate Professor, University of Foggia, Foggia, Italy
Written by: Zachary Klaassen, MD, MSc – Urologic Oncologist, Associate Professor of Urology, Georgia Cancer Center, Wellstar MCG Health, @zklaassen_md on Twitter during the 2024 European Society of Medical Oncology (ESMO) Annual Meeting, Barcelona, Spain, Fri, Sept 13 – Tues, Sept 17, 2024.
Related content: RAPSON Trial Explores Radium223 and Docetaxel Sequencing in mCRPC - Vincenza Conteduca