(UroToday.com) The 2025 American Society of Clinical Oncology Genitourinary (ASCO GU) cancers symposium held in San Francisco, CA was host to the Poster Session A: Prostate Cancer. Dr. Osama Mohamad presented Abstract 254: The prognostic impact of prostate-specific antigen at 6 months after post-prostatectomy radiotherapy: An individual patient data analysis of two NRG oncology randomized trials.
Dr. Mohamad began by emphasizing the study’s goal: to assess the prognostic significance of PSA levels within six months after completing salvage radiotherapy (RT) in patients treated with RT alone or in combination with hormone therapy.
The investigators analyzed individual patient data from two randomized trials, NRG’s RTOG 0534 and RTOG 9601, which evaluated salvage RT with or without hormone therapy. Hormone therapy consisted of either 4–6 months of ADT or 2 years of bicalutamide. The lowest PSA recorded within six months post-RT was identified and categorized as ≤0.1 ng/mL or >0.1 ng/mL.
The primary outcomes of the study were metastasis-free survival (MFS) and overall survival (OS). The investigators used multivariable Cox proportional hazards regression to estimate hazard ratios (HRs) with 95% confidence intervals, assessing the association between PSA levels within six months post-RT and both OS and MFS. The analysis was adjusted for age, Gleason score, trial, and hormone therapy use.
Dr. Mohamad reported that among the 2,373 patients included in the analysis, 1,833 (77%) achieved a nadir PSA ≤0.1 ng/mL, while 540 (23%) did not. Among those who did not receive hormone therapy, 50% failed to reach this milestone, compared to only 6% of patients who received hormone therapy.
Notably, achieving a PSA ≤0.1 ng/mL was associated with significantly improved OS (HR 0.27 [95% CI 0.12-0.6], p=0.001) and MFS (HR 0.25 [95% CI 0.13-0.47], p<0.0001).
The investigators conducted an interaction test, which revealed that the survival benefit associated with achieving a PSA nadir ≤0.1 ng/mL was more pronounced in patients who did not receive hormone therapy compared to those who did.
The five-year MFS rates for patients receiving RT alone, RT+ADT and RT+bicalutamide based on PSA ≤0.1 vs. >0.1 ng/mL status were 94% vs. 81%, 92% vs. 87%, and 91% vs. 93%, respectively, Similarly, the ten-year OS rates for these groups were 87% vs. 76%, 84% vs. 84%, and 82% vs. 83%, respectively.
Dr. Mohamad concluded his poster with the following takeaways:
- PSA >0.1 ng/mL within 6 months was prognostic for OS and MFS in patients treated with salvage RT in the post-prostatectomy setting.
- Among patients who did not receive hormone therapy, 50% failed to reach a PSA ≤0.1 compared to only 6% of patients who received hormone therapy.
- The survival benefit associated with achieving a PSA nadir ≤0.1 ng/mL was more pronounced in patients who did not receive hormone therapy compared to those who did.
- This finding allows better patient counseling and can guide clinical trial design for treatment intensification or de-intensification in patients receiving salvage RT.
Presented by: Osama Mohamad, MD, Department of Radiation Oncology, The University of Texas MD Anderson Cancer Center. Houston, TX.
Written by: Julian Chavarriaga, MD – Urologic Oncologist at Cancer Treatment and Research Center (CTIC) via Society of Urologic Oncology (SUO) Fellow at The University of Toronto. @chavarriagaj on Twitter during the 2025 Genitourinary (GU) American Society of Clinical Oncology (ASCO) Annual Meeting, San Francisco, CA, Thurs, Feb 13 – Sat, Feb 15, 2025.