3478 - Long-Term Outcomes After Stereotactic Radiation Therapy for Head and Neck Cancers with Perineural Spread
Presenter(s)
C. D. Goodman1, A. Lawless2, T. P. Nguyen3, A. S. Garden4, H. Wang5, X. A. Wang6, A. Lee4, J. P. Reddy7, A. C. Moreno4, M. T. Spiotto4, C. D. Fuller8, D. I. Rosenthal4, M. Migden9, N. D. Gross10, S. Y. Su10, E. Y. Hanna11, and J. Phan4; 1Department of Oncology, Western University, London, ON, Canada, 2MD Anderson Cancer Center, Houston, TX, 3The University of Texas MD Anderson Cancer Center, Houston, TX, 4Department of Radiation Oncology, The University of Texas MD Anderson Cancer Center, Houston, TX, 5Department of Radiation Physics, The University of Texas MD Anderson Cancer Center, Houston, TX, 6Department of Radiation Physics, University of Texas MD Anderson Cancer Center, Houston, TX, 7Department of Radiation Oncology, University of Texas MD Anderson Cancer Center, Houston, TX, 8Division of Radiation Oncology, The University of Texas MD Anderson Cancer Center, Houston, TX, 9University of Texas MD Anderson Cancer Center, Houston, TX, 10Department of Head and Neck Surgery, The University of Texas MD Anderson Cancer Center, Houston, TX, 11Department of Head and Neck Surgery, University of Texas MD Anderson Cancer Center, Houston, TX
Purpose/Objective(s):
Perineural spread (PNS) in head and neck cancer (HNC) is associated with poor prognosis and presents technical challenges due to complex target volumes that track along nerve pathways in proximity to critical organs at risk. Stereotactic radiation therapy (SBRT) has demonstrated favorable local control and toxicity profiles in recurrent and/or unresectable HNC, but data specific to PNS are lacking. We evaluated oncologic outcomes and toxicity of SBRT for HNC with PNS, with particular attention to histologic-specific patterns of failure.Materials/Methods:
A retrospective cohort study was conducted at two sites (US and Canada) under Institutional Review Board approval with waiver of informed consent. All patients treated with SBRT for PNS of HNC between January 2015 and August 2025 comprised the study cohort. Data cut off was December 31, 2025. Primary endpoints were overall survival (OS), progression-free survival (PFS), and locoregional recurrence-free survival (LRFS), defined from RT start and estimated using Kaplan-Meier methods. Clinical, treatment, toxicity (CTCAE v5.0), and outcome data were extracted from electronic medical records.Results:
Thirty-seven patients met inclusion criteria. Median age was 66 years (range 31-80) and 20 were male (54%). Histologies included 18 cutaneous squamous cell carcinoma (cSCC, 49%), 10 adenoid cystic carcinoma (ACC, 27%), and 9 other histologies (24%). Two patients had distant disease at time of SBRT, and 27 patients (73%) had received prior high dose RT, with median interval of 25 months (range 5-157). Median SBRT dose was 42.5 Gy (range 27-45), in median 5 fractions (range 3-5), with treatment delivered every second day. Twenty-one patients (57%) had systemic therapy in combination with SBRT, delivered as induction (32%), concurrent (32%) and adjuvant (19%). Median follow up was 47 months (95% CI 41-51). Median OS, PFS, and LRFS are reported in the Table. PFS and LRFS estimates were significantly longer for cSCC compared to ACC and other histologies (log-rank test p=0.022 and p=0.006 respectively). Fourteen patients had locoregional failure (LRF) of which two cases were within the high dose volume (both ACC). Abbreviations: Not estimable (NE) There were no acute grade 3 or higher toxicities. Ten patients (27%) had late grade 3 or higher toxicities (CTCAE V5). Radiographic temporal lobe necrosis occurred in 13 patients (35%) of which 3 (8%) were symptomatic. Osteoradionecrosis occurred in 9 patients (24%) with 4 (11%) symptomatic.Conclusion:
SBRT for HNC with PNS provides durable local control, particularly for cSCC. ACC demonstrated higher risk of in-field failure compared with cSCC.| Histology | |||
| Survival (months) | PFS | LRFS | |
| cSCC (N=18) | 61.9 (95% CI NE) | 61.9 (95% CI 19.9, 103.8) | 94.4 (95% CI NE) |
| ACC (N=10) | 43.2 (95% CI 34.6-51.9) | 11.2 (95% CI 0, 26.3) | 24.6 (95% CI 0-53.145) |
| Other (N=9) | Median OS not reached | 10.3 (95% CI 4.0, 16.5) | 12.4 (95% CI 9.3-15.5) |
| Total (N=37) | 61.9 (95% CI NE) | 32.5 (95% CI 7.0, 58.0) | 77 (95% CI 19.3-134.7) |