2785 - Safety and Efficacy of Postoperative Stereotactic Body Radiotherapy for Newly-Diagnosed or Recurrent Head and Neck Cancer

Purpose/Objective(s): Stereotactic body radiotherapy (SBRT) is infrequently used in the adjuvant setting after surgical resection of head and neck cancer (HNC) though may be preferred by some patients due to its shorter course and possibly improved tolerability. Data on the use of postoperative SBRT in HNC are limited, particularly for patients with newly diagnosed disease. This study evaluates treatment patterns, toxicity, and recurrence patterns in patients receiving adjuvant SBRT for newly diagnosed or recurrent HNC.

Materials/Methods: This is a single-institution, retrospective cohort study of patients with newly diagnosed or recurrent HNC who underwent postoperative SBRT 2016 to 2024. Patient demographics, tumor characteristics, treatment details, and clinical outcomes were collected and compared. Key endpoints included grade =3 CTCAE toxicity, recurrence patterns, and HNC-specific mortality.

Results: A total of 41 SBRT courses (17 [41.5%] new, 24 [58.5%] recurrent diagnoses) in 40 patients were analyzed, with a median follow-up of 20.1 months (IQR 7.6-29.3) from SBRT. The mean age and median ECOG performance status at SBRT were 71 years and 1, respectively. The median pT stage was 3 and the median pN stage was 0. 12 (29.3%) cases had positive margins, and 13 (31.7%) had extranodal extension. The most common primary site was oral cavity (17 [41.5%]), and 22 (53.7%) cases were squamous cell carcinomas. Among recurrent cases, 18 (72%) had received prior radiotherapy (median dose 70 Gy; median fractions 33; median interval from prior radiotherapy 18 months). The median interval from surgery to SBRT was 54 days (IQR 43-64). The median SBRT dose was 30 Gy (range 25-55 Gy), and all courses were 5 fractions. The mean planning target volume (PTV) size was 123cc (standard deviation 124cc). 15 (36.6%) courses included a boost to high risk areas. The mean boost volume was 60cc and median dose was 40 Gy. Concurrent systemic therapy was administered in 13 (13.7%) cases. There were no acute grade 3 toxicities, and there were 2 (4.9%) late grade 3 toxicities; one in a newly-diagnosed patient and one with prior HNC radiotherapy. 21 (51.2%; 11 new, 10 recurrent) patients experienced any recurrence, of which 11 (52.4%) were locoregional, 6 (28.6%) were distant, and 4 (19.0%) were both. The 2-year cumulative incidences of locoregional recurrence, any recurrence, and HNC-specific mortality were 33.3% (95% confidence interval [CI] 18.9-48.3), 46.3% (95% CI 29.7-61.5), and 37.7% (95% CI 22.1-53.3), respectively. The rates of locoregional recurrence, any recurrence, and HNC-specific mortality were not significantly different between new and recurrent cases.

Conclusion: Adjuvant SBRT demonstrated acceptable toxicity albeit with considerable recurrence rates in patients with newly diagnosed or recurrent HNC. Further research is needed to optimize patient selection and treatment strategies.