KEY POINTS
- ARGOS-CLIMBER enrolled 50 men with unfavorable-intermediate to very-high-risk prostate cancer; median age was 73 years and median follow-up 3.0 years. Forty-six percent had unfavorable-intermediate-risk, 46% high-risk, and 8% very-high-risk disease.
- Treatment planning incorporated hybrid 18F-PSMA PET and multiparametric MRI. Five-fraction VMAT delivered 25 Gy to the pelvis, 35 Gy to the prostate, and 35 Gy to PET-positive nodes, with a planned simultaneous intraprostatic boost toward 50 Gy when OAR constraints permitted.
- ADT started after SABR and was planned for 6 months in unfavorable-intermediate-risk disease and 18 months in high-risk disease.
- PSMA PET response continued to deepen after treatment, reaching a complete response rate of approximately 67% at two years. The authors emphasize that post-treatment PSMA PET and MRI remain exploratory response biomarkers rather than validated surrogates.
- Only two biochemical failures were reported, both accompanied by metastatic progression. Three-year overall survival was 88.9% (95% CI 75.2–95.3) and prostate cancer-specific survival 95.7% (95% CI 83.8–98.9).
- Late GU toxicity was limited: 5/50 patients (10%) developed grade 2 GU adverse events and none had grade 3–4 late GU toxicity. No grade 2–3 late GI events occurred, but one patient experienced a grade 4 rectal complication requiring colostomy after treatment of an angiodysplastic lesion with argon plasma coagulation.
- There is still no randomized evidence establishing the value of an intraprostatic boost specifically within prostate SABR. The small cohort, few oncologic events, and exploratory imaging analyses limit conclusions about efficacy or biomarker-guided escalation.
CLINICAL TAKEAWAY
Five-fraction pelvic SABR with PSMA/MRI-defined focal escalation appears feasible in unfavorable-risk prostate cancer and produced encouraging biochemical and imaging responses. These phase 1/2 results support further study rather than establishing focal-boost SABR as a new standard.