Kuncman, Łukasz

Background Stereotactic body radiotherapy (SBRT) is increasingly used for patients with oligometastatic prostate cancer, yet the optimal target definition, dose, and toxicity profile for rib metastases remain uncertain. Objectives We assessed local control (LC), toxicity, and the risk of radiation-induced rib fracture (RF) after SBRT for rib metastases. Design Retrospective multicenter cohort study. Methods We analyzed prostate cancer patients with radiologically diagnosed rib metastases treated with SBRT and >=12 months of follow-up. Outcomes were descriptively compared between gross tumor volume (GTV)-only and GTV plus an intraosseous clinical target volume (CTV) margin. Analyses included Kaplan-Meier survival estimates, cumulative incidence functions, and exploratory univariable Cox and logistic regression; no formal equivalence testing or multivariable validation was attempted because event numbers were very low. Results We included 102 patients with a median follow-up of 20 months. The 1- and 2-year LC rates were 97.9% and 96.3%, respectively. At 3 years, local progression was 2.1% in the GTV-only group, absent in patients treated with >=10 mm margins, and numerically highest with 3-5 mm CTV margins (13.5%, p=0.022). Among 13 symptomatic patients, pain control was excellent, with complete or partial response in all patients within 6 months. No grade >=3 toxicities occurred. RFs were rare (n=3, 2.9%), comprising one symptomatic Grade 2 event (0.9%) and two asymptomatic Grade 1 events (2.0%). Baseline symptoms and extraosseous infiltration were associated with RF in exploratory univariable analysis, but confidence intervals were wide. Higher PTV dose exposure, particularly PTV D50% (36.9 vs. 31.1 Gy, p=0.041), was also observed among RF cases. Conclusions SBRT for rib metastases from prostate cancer was associated with high LC, pain relief, and low observed toxicity in this retrospective real-world cohort. GTV-only contouring may be feasible in carefully selected patients staged and planned with PSMA-PET/CT, but the non-randomized design, baseline imbalances, short follow-up, and very low event count preclude drawing conclusions about equivalence or independent validation. RF predictor analyses should be considered exploratory and hypothesis-generating.

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.