3688 - Comparative Toxicity and Outcomes of IMRT vs. SBRT for Re-Irradiation in Head and Neck Squamous Cell Carcinoma

Purpose/Objective(s):

Re-irradiation remains a key component in treatment of locoregionally recurrent or second primary head and neck squamous cancers (HNSCC). Herein, we seek to compare intensity modulated radiation therapy (IMRT) and stereotactic body radiotherapy (SBRT) for re-irradiation of recurrent or second primary HNSCC, evaluating locoregional control (LRC), overall survival (OS), and acute and late toxicity in a retrospective cohort, with the aim of informing modality selection and optimizing patient outcomes.

Materials/Methods:

After IRB approval, an institutional database was queried for patients with locoregionally recurrent or second primary squamous cancers of the head and neck. Inclusion criteria included patients previously treated with =40 Gy to the head and neck and then received curative intent IMRT or SBRT. Patients were excluded if non-squamous histology, M1 status, or no gross tumor volume (GTV). Demographic, prior treatment, and current treatment factors were abstracted from the charts. Toxicities were graded per the CTCAE Version 4. Differences in acute and late toxicities were compared via Pearson’s Chi-Squared. Locoregional control (LRC) and overall survival (OS) were measured from start of treatment and analyzed via Kaplan-Meier Curve and log-rank test

Results:

This study included 199 patients available for analysis, with 102 in the IMRT cohort and 97 in the SBRT cohort. Median follow up for patients alive at last contact was 41.5 months. Median BED10 of entire cohort was 72 Gy (range 28.8 – 84 Gy). Of 199 patients available for acute toxicity analysis, IMRT was associated with a higher rate of grade 3-5 acute toxicity, 45.1% vs 8.2% (p<0.001). Of 193 patients available for late toxicity analysis, there was no significant difference in late grade 3–4 toxicity between SBRT and IMRT, 30.2% vs 24.7% (p=0.395). There was no significant difference in LRC between the groups with 2-year LRC of 35.0% for IMRT and 34.4% for SBRT (p=0.595), nor for 2-year OS of 33.2% for IMRT and 33.2% for SBRT (p=0.793). When stratified by median GTV (13.86 cc, range 0.53 – 139.63 cc), there was no significant difference in OS between patients treated with SBRT versus IMRT.

Conclusion:

SBRT re-irradiation for locoregionally recurrent or second primary HNSCC was more tolerable in the acute setting, without significant difference in late toxicity, LRC, or OS. Further work is necessary to improve outcomes and reduce late toxicity in this high risk population.