(UroToday.com) The 2025 GU ASCO annual meeting featured a prostate cancer session and a presentation by Dr. Jesus Casillas discussing a pooled analysis of SOLAR and SATURN clinical trials comparing progression following systemic and tumor-directed therapy for de novo versus recurrent PSMA PET–defined oligo-M1 prostate cancer. Oligometastatic castration sensitive prostate cancer (CSPC) presents a unique opportunity for curative or long term disease control through targeted and systemic therapies. Emerging studies favor a multimodal approach, combining treatment of the primary and metastases with short term intensified systemic therapy, aiming to improve survival and local control while minimizing toxicity from indefinite systemic therapy. This post-hoc analysis of the SOLAR (NCT03298087) and SATURN (NCT03902951) trials, which evaluated systemic and tumor-directed therapy in PSMA-PET defined oligo-M1 (≤5 metastases) de novo and recurrent oligometastatic CSPC, respectively, aims to draw inferences on biology and oncologic outcome.
All patients were treated with 6 months of systemic therapy: leuprolide, abiraterone acetate with prednisone, and apalutamide in conjunction with SBRT to oligometastatic sites. SOLAR patients were treatment naïve and underwent either radical prostatectomy with lymph node dissection followed by post-operative radiotherapy for high-risk features, or definitive radiotherapy. SATURN patients all had recurrent disease after radical prostatectomy with or without postoperative radiotherapy and may have also had prior hormone or metastasis-directed therapy. The SOLAR and SATURN trial schemas are highlighted as follows:
The primary endpoint (response rate) was the percentage of patients with an undetectable PSA (<0.05 ng/mL) for post-radical prostatectomy patients, or a PSA <2 ng/mL for post-definitive radiotherapy patients, six months after recovery of testosterone to >150 ng/dl. Secondary endpoints included progression free survival and eugonadal progression free survival starting from time of testosterone recovery.
This analysis included data from 24 SOLAR and 26 SATURN patients. Overall, the median follow-up was 32 months (IQR 28.25-36.75 months). Response rates were higher for de novo versus oligorecurrent patients (20/24 [83%] versus 13/26 [50%], p = 0.018). Median and eugonadal progression free survival were longer for the de novo group (NR versus 17 months and NR versus 13 months, p < 0.05):
Progression free survival was shorter for oligorecurrent patients with prior exposure to hormone therapy (median 10 months versus NR, p < 0.0001):
There was no progression free survival difference comparing patients treated in the de novo setting versus the recurrent setting who were naive to hormonal therapy (p = 0.23):
There were 9 SATURN patients enrolled at first recurrence and showed no progression free survival difference from the SOLAR cohort (p = 0.18):
Dr. Casillas concluded his presentation discussing a pooled analysis of SOLAR and SATURN clinical trials comparing progression following systemic and tumor-directed therapy for de novo versus recurrent PSMA PET–defined oligo-M1 prostate cancer with the following take-home points:
- Patients with molecular PET-defined oligometastatic prostate cancer, treated with comprehensive primary and metastasis directed therapy combined with short term intensified systemic therapy, may achieve durable disease free status with restored testosterone levels and without ongoing active treatment
- Recurrence oligometastatic CSPC had worse outcomes than the de novo oligorecurrent patients, likely due to prior hormonal therapy exposure leading to progressive treatment resistance
Presented by: Jesus E. J. Casillas, MD, Department of Radiation Oncology, University of California, Los Angeles, Los Angeles, CA
Written by: Zachary Klaassen, MD, MSc – Urologic Oncologist, Associate Professor of Urology, Georgia Cancer Center, Wellstar MCG Health, @zklaassen_md 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.