Outcomes of stereotactic body radiotherapy for supraclavicular lymph node metastasis among patients with metastatic prostate cancer

Purpose/objectives: Metastasis directed therapy (MDT) with stereotactic body radiotherapy (SBRT) has demonstrated clinical benefit among select oligometastatic prostate cancer (PCa) patients. The outcomes of SBRT to the left supraclavicular lymph nodes (SCLNs) are examined. Materials/methods: Between 2017 and 2024, 16 (3.8%) of 419 patients with PCa metastatic to lymph nodes were found by prostate-specific PET to have SCLN involvement. Survival, relapse patterns, and toxicity are analyzed. Results: At initial PCa diagnosis, median PSA was 6.7 ng/mL (range 2.1-315) with 50% of patients having Gleason score of 8-10. Mean time from initial diagnosis to SCLN metastasis was 10.4 years with median PSA of 2.0 ng/mL and median number of involved SCLNs of 1.5 (range 1-10). The most common fractionation scheme was 35 Gy in 5 fractions daily (44%) with 81% of patients receiving concurrent hormonal therapy. No grade ≥ 2 toxicities were reported. Local relapse-free survival at 5 years was 90.9%. Mean distant progression-free survival was 16.7 months (95% CI: 7.9-25.5). Mean prostate cancer-specific survival (PCSS) and overall survival were 4.6 years (95% CI: 3.6-5.6) and 4.0 years (95% CI: 2.8-5.1), respectively. Patients with castration-sensitive disease had 100% 5-year PCSS, and 58.3% for those with mCRPC. Conclusion: SBRT to SCLNs was well tolerated with no significant toxicity. Durable local control was satisfactory. The presence of SCLN metastases is frequently a harbinger of additional metastatic progression which suggests that patients require close monitoring and could benefit from the addition or intensification of systemic therapy.