Outcomes of Radiotherapy With or Without Dose Escalation to Lymph Node Metastases Detected by PET PSMA or Conventional Imaging in Node-Positive Prostate Cancer

PURPOSE: To evaluate the impact of PSMA PET versus conventional imaging for staging, and the effect of dose escalation (DE) to metastatic lymph nodes in cN1 prostate cancer patients treated with EBRT and ADT. METHODS: A retrospective multicenter analysis included 197 propensity score-matched patients (77 staged with PSMA PET, 120 with conventional imaging) treated with EBRT and ADT, with or without DE to lymph node metastases. Matching criteria were T stage, nodal involvement, imaging modality, Gleason score, and ADT duration. Primary endpoint was metastasis-free survival (MFS); secondary endpoints included overall survival (OS), locoregional control (LRC), and toxicity. RESULTS: Median follow-up was 42 months (IQR: 25-59). Median EQD2 (alpha/beta=1.5) to elective nodes was 46 Gy, and to metastatic nodes, 66 Gy (PSMA PET) and 63 Gy (conventional imaging). The 3-year MFS was 80.5% (95% CI: 71.3-90.8%) for PSMA PET and 77.2% (95% CI: 69.5-85.8%) for conventional imaging; 5-year MFS was 59.3% versus 65.8% (P=0.57). OS at 5 years was 82.2% (PSMA PET) and 77.4% (conventional imaging) (P=0.72). On multivariable analysis, ISUP grade group 3-5 predicted earlier metastasis (HR: 4.03, 95% CI: 1.61-10.06; P=0.003); higher prostate dose (EQD2 ≥113 Gy) improved MFS (HR: 0.53, 95% CI: 0.30-0.95; P=0.033); long-term ADT (≥24 mo) improved OS (HR: 0.38, 95% CI: 0.19-0.78; P=0.009). No significant difference in toxicity was observed between groups. CONCLUSIONS: PSMA PET staging and nodal dose escalation >60 Gy were safe but did not improve MFS, OS, or LRC. ISUP grade group 3-5 and higher prostate dose significantly influenced outcomes.