e17505 Background: Stereotactic body radiotherapy (SBRT) has been shown to provide locoregional control in head and neck squamous cell carcinoma (HNSCC) patients (pts) who are not candidates for curative procedures due to poor performance status, comorbidities, or radiation dose limitations from prior treatment. The addition of chemotherapy (chemo) and/or cetuximab (CET) is hypothesized to improve outcomes compared to SBRT alone, but there is limited data on comparative effectiveness. We compared outcomes of pts treated with SBRT vs. SBRT + chemo and/or CET using retrospective observational data from our institution. Methods: We identified new and recurrent HNSCC pts treated with SBRT +/- systemic therapy from 2012 to 2018. Age, Charlson Comorbidity Index (CCI) and stage were recorded. Primary outcome was locoregional disease control rate based on Modified Response Evaluation Criteria in Solid Tumors on 3-month post-treatment imaging. Secondary outcome was overall survival (OS) at 1 year. Pts were divided into 4 groups: SBRT, SBRT+chemo, SBRT+CET, and SBRT+chemo+CET (cohorts A, B, C and D, respectively). Results: 90 pts with median age of 73 years and median follow-up of 11.5 months were included. 94.4% were stage III or IV, and 68.9% had recurrent disease. The most commonly utilized chemotherapy was carboplatin and paclitaxel. Cohorts A, B, C and D constituted 28.9%, 31.1%, 31.1% and 8.8% respectively. Groups were well matched except for pts in Cohort A being significantly older than those in Cohort B (74.9 vs. 68.4 years; p = 0.01). Average CCI estimated 10-year survival was 8.4%. There was a trend towards improved locoregional control at 3 months in Cohort B vs. A (57.1% vs. 34.6%, p = 0.09), and improved OS at 1 year (46.4% vs. 23.1%; p = 0.07). These trends were not observed in comparisons between other cohorts. Conclusions: Chemo + SBRT may improve disease control as well as 1 year OS in HNSCC pts who do not qualify for curative procedures. Given the younger age of pts receiving chemo, selection bias cannot be excluded. Prospective studies with larger patient cohorts are needed to further evaluate the benefits and toxicities of adding systemic treatment to SBRT in this population.
Prediction of Locoregional Control in Head and Neck Squamous Cell Carcinoma with Serial CT Perfusion during Radiotherapy
