3484 - Intraoperative Cs-131 Brachytherapy after Salvage Resection for Recurrent/High-Risk Head & Neck Cancer in Frail Patients: A Contemporary Comparison with RTOG 9610

Purpose/Objective(s): Management of locally recurrent or high-risk head and neck squamous cell carcinoma (HNSCC) in elderly or medically fragile patients remains challenging. RTOG 9610 evaluated hyperfractionated re-irradiation (60 Gy in 1.5 Gy BID fractions) with concurrent chemotherapy for unresectable recurrent disease and reported a 12-month overall survival (OS) of 42%, grade =3 toxicity of 62%, and treatment-related mortality (TRM) of 7.4%. The optimal re-irradiation strategy after salvage surgery in frail patients is undefined. We evaluated feasibility, toxicity, and efficacy of intraoperative cesium-131 (Cs-131) brachytherapy in this population and compared outcomes with RTOG 9610 benchmarks.

Materials/Methods: This prospective single-institution cohort included patients with recurrent or high-risk HNSCC undergoing maximal gross resection followed by intraoperative Cs-131 implantation to the tumor bed (70–80 Gy prescribed to 5 mm depth). Outcomes included 12-month OS, locoregional control (LRC), local control (LC), cumulative grade =3 radiation-associated toxicity (CTCAE), and TRM. Comparisons with published RTOG 9610 outcomes were performed using Chi-square and Fisher’s exact tests.

Results: Between 2020–2026, 16 patients underwent 16 implants. Median age was 72 years (vs 62 years in RTOG 9610, p<0.01). Twelve patients had locally recurrent disease and four had high-risk primary disease. Eleven patients (69%) had prior radiation to the operative field; median interval from prior RT was 32 months (range 6–182). Median implant dose was 70 Gy using a median of 28 seeds. With median follow-up of 11 months, no grade =3 toxicities or TRM were observed. Four patients developed grade 2 toxicity only. Five patients experienced locoregional recurrence (2 local). Twelve-month LC and LRC were 83% and 69%, respectively. Median OS was not reached; 12-month OS was 52%. Compared with RTOG 9610: 12-month OS: 52% vs 42%, Grade =3 toxicity: 0% vs 62%, TRM: 0% vs 7.4%.

Conclusion: Intraoperative Cs-131 brachytherapy following salvage resection demonstrates encouraging local control with markedly reduced severe toxicity compared with hyperfractionated chemoradiation in RTOG 9610, despite an older and frailer population. These findings suggest Cs-131 may represent a lower-morbidity re-irradiation strategy for surgically managed recurrent/high-risk HNSCC and warrant validation in multi-institutional prospective studies.