The CYGNUS multicenter retrospective study collected 155 SBRT reirradiations across 150 patients with metachronous pelvic node oligomets from castration sensitive prostate cancer. All recurrences overlapped with prior radiation fields. The majority (80.7%) had undergone radical prostatectomy followed by prostate bed RT (median 66 Gy), and 56.7% had also received prior pelvic nodal RT (median 46–50 Gy). SBRT was delivered to a median dose of 33 Gy in 5 fractions. Notably, the vast majority of centers did not perform plan summation, reasoning that pelvic organ position would differ sufficiently between courses, though this left cumulative OAR doses essentially unknown. The OAR doses from reirradiation alone were modest (median rectal D2cc EQD2 2.4 Gy, bladder 2.6 Gy), suggesting that the nodes selected for SBRT sat relatively far from critical structures. At a median follow-up of 30.5 months, late grade ≥2 GU adverse events was 9.7% (grade 3 in 2.6%), with late grade 2 GI AEs at just 1.9% and no grade ≥3 GI events. Oncologically, the 2-year rPFS was 44.6% and 2-year ADT-free survival was 52.6%, consistent with prior SBRT-alone series and notably inferior to the 3-year rPFS of 90% seen with elective nodal RT in STORM PEACE-V. Indeed, the dominant relapse pattern was further pelvic nodal disease (42.5%). | Anger, Int J Radiat Oncol Biol Phys 2026
