3690 - Association of Biologically Effective Dose and Survival in Patients Receiving Head and Neck Stereotactic Body Radiation Therapy

C. Márquez¹, J. Phan², A. Lee², J. Reddy³, A. S. Garden², G. B. Gunn², S. J. Frank², C. D. Fuller³, A. C. Moreno³, W. H. Morrison², D. I. Rosenthal², and M. T. Spiotto²; ¹MD Anderson Cancer Center, Houston, TX, ²The University of Texas MD Anderson Cancer Center, Houston, TX, ³Department of Radiation Oncology, The University of Texas MD Anderson Cancer Center, Houston, TX

Purpose/Objective(s):

Stereotactic body radiation therapy (SBRT) is an emerging approach for treating recurrent head and neck cancers (HNCs) and uses various fractionation schemes. However, limited data exists comparing the biologically effective doses (BEDs) of SBRT fractionation schemes and patient outcomes. Here, we hypothesized that higher BED was associated with improved survival in HNC patients treated with SBRT.

Materials/Methods:

Utilizing the National Cancer Database, we identified 455 M0 patients with HNC treated with SBRT. SBRT was defined as a total dose of 20-50 Gy delivered in = 6 fractions ranging from 5-10 Gy per fraction. BEDs were calculated using an a/ß ratio of 10. Factors associated with BED were analyzed using logistic regression, and patients were stratified into BED < 50 Gy (BED50; n = 181), 50-80 Gy (BED50-80; n = 196), and > 80 Gy (BED80; n = 78). Overall survival was analyzed using Kaplan–Meier and Cox regression models.

Results:

The most commonly treated sites included oropharynx (38.2%), oral cavity (22.0%), and larynx (14.7%), with the remainder of sites being hypopharynx, nasopharynx, paranasal sinus, and salivary. There was no difference in sex, HPV-status, performance status, T-stage, N-stage, or use of surgery or chemotherapy across groups. Of note, 110 patients (24.2%) underwent surgery prior to radiation. Median follow-up duration was 11.1 months (m). Multivariate analysis revealed survival associations with BED50-80 (HR = 0.70, p=0.007), surgery (HR = 0.56, p=0.001), age > 70y (HR = 1.74, p=0.049), N-stage 2-3 (HR = 1.41, p=0.022) and performance status (Charlson–Deyo 2 vs 0–1: HR = 2.19, p=0.003). In patients not undergoing surgery, higher BEDs correlated with improved median survival (BED50 = 7.8m vs. BED50-80 = 14.6m vs. BED80 = 10.1m; P=0.0001). Conversely, patients treated with initial surgery showed no survival improvement with increasing BED (p=0.4503).

Conclusion:

In HNC patients, higher BEDs in SBRT regimens were associated with enhanced survival among those with intact disease, in contrast to the absence of a survival advantage in surgically resected patients. These findings suggest that higher-dose SBRT regimens are critical for intact disease, while adjuvant SBRT regimens do not require dose escalation.