Main Session

Sep 29

PQA 07 - Head and Neck Cancer, Lung Cancer/Thoracic Malignancies, and Nursing and Supportive Care

3495 - Evaluating Adaptive SBRT for Head and Neck Malignancies: Practice Patterns, Toxicity, and Outcomes

03:45pm - 05:00pm ET

Poster Hall - Exhibit Hall A

Screen: 4

POSTER

Presenter(s)

Jared Hobson, MD, BSN, RN - Mayo Clinic Rochester, Rochester, MN

J. N. Hobson¹, D. K. Ebner¹, D. J. Ma¹, T. D. Malouff¹, D. M. Routman¹, J. M. Wilson¹, T. Morris¹, V. Malkov¹, R. J. Brisson², T. J. Patton¹, M. Neben Wittich¹, and S. C. Lester¹; ¹Department of Radiation Oncology, Mayo Clinic, Rochester, MN, ²Department of Radiation Oncology, University of Florida College of Medicine, Gainesville, FL

Purpose/Objective(s):

While early studies of stereotactic body radiotherapy (SBRT) in the head and neck (H&N) suggest favorable local control, toxicity concerns have limited uptake, particularly with re-irradiation or complex anatomy. Adaptive radiotherapy may improve safety by accounting for anatomic change and tumor regression. We compare adaptive and non-adaptive H&N SBRT to inform practice patterns, toxicity, and outcomes.

Materials/Methods:

We performed a retrospective review of all patients treated with H&N SBRT at a single institution from 2015 - 2025. Data included demographics, ECOG performance status, histology, HPV status, treatment site, prior therapies, modality, dose, fractionation, adaptive use, and concurrent systemic therapy. Endpoints included symptom and objective response, acute and late toxicity (CTCAE v5.0), local control (LC), progression-free survival (PFS), overall survival (OS), and cause of death.

Results:

45 patients underwent 48 SBRT courses, including 14 adaptive (13 patients) and 34 non-adaptive courses (33 patients). Median age (71 vs 68 years) and ECOG =2 rates (15% each) were similar, though adaptive SBRT patients had shorter median follow-up (5.1 vs 9.4 months). Adaptive SBRT was more often used for secondary-site targets (71% vs 32%, p=0.024) and less often for re-irradiation (28.6% vs 50.0%). Median delivered dose was 42.5 Gy (adaptive) versus 40 Gy (non-adaptive), both in 5 fractions. Adaptive SBRT was predominantly delivered every 10–14 days (85.7%), whereas non-adaptive SBRT was commonly delivered every other day (47.1%) followed by daily (14.7%) and 10-14 days (14.7%). Median PFS was shorter in the adaptive cohort (116 vs 167 days, p=0.0167), while 1-year LC (53.3% vs 66.9%, p=0.68) and OS (67.5% vs 58.2%, p=0.40) were similar. Acute grade =3 toxicity occurred in 21.4% of adaptive and 5.9% of non-adaptive courses (p=0.14), while late grade =3 toxicity was comparable (28.6% vs 20.6%). Concurrent systemic therapy was associated with increased acute grade =3 toxicity (p=0.037). No flap failures occurred. Grade =4 events were rare, with one grade 5 osteonecrosis following non-adaptive SBRT re-irradiation. Deaths were predominantly disease-related.

Conclusion:

H&N SBRT appears safe and well tolerated, with adaptive planning achieving comparable local control and late toxicity to non-adaptive treatment. Patients with challenging clinical target volumes and scenarios often selected for adaptive therapy in order to gain temporal data on response and competing risk of distant progression. Higher rates of acute toxicity and shorter PFS in the adaptive cohort likely reflect patient selection rather than treatment-related harm. These findings support adaptive SBRT as a safe and rational strategy for selected H&N patients, with longer-term outcomes pending larger cohorts and mature follow-up.