Analysis of Stereotactic Body Radiotherapy for Head and Neck Cancer using the National Cancer Database

Abstract

Recent studies have demonstrated promising results with stereotactic body radiation therapy (SBRT), usually as re-irradiation in recurrent head and neck cancer (HNC) or second primary HNC, and in patients who cannot tolerate 6-7 weeks of conventional radiotherapy. We seek to evaluate the uptake of SBRT for HNC using the National Cancer Database (NCDB) and evaluate social, clinicopathological and treatment factors impacting overall survival (OS). To evaluate the national utilization of SBRT for head and neck cancer and investigate the relationship between social demographics, clinicopathological factors, and treatment dose fractionation with overall survival. The NCDB was queried to identify 549 HNC cases undergoing SBRT from 2004 to 2015. Patients were treated in 1 (15-24Gy, n=46), 2 (7.5-12Gy, n=19), 3 (5-12Gy, n=57), 4 (5-12Gy, n=34), or 5 (4-10Gy, n=393) fractions. The biologically effective dose with α/β=10 (BED10) was calculated. A BED10 of 59.5 Gy10 using a dose/fractionation scheme of 35 Gy in 5 fractions was used as a cut point to evaluate SBRT effective dose regimens on survival. The following patient factors were analyzed: age, race, insurance status, median household income, and Charlson-Deyo Score (CDS), year of diagnosis, TNM stage category, history of cancer, and tumor site (larynx/hypopharynx, oral cavity/oropharynx/lip, sino-nasal/nasopharynx, salivary gland). Treatment factors included BED10 (<59.5 Gy10, ≥59.5 Gy10), facility type, and treatment modality (radiation only, RT; chemoradiation, CRT; surgery with radiation, S+R; surgery with chemoradiation, S+CRT). Median OS, three, and five-year survival rates were estimated using the Kaplan-Meier method. Cox proportional hazards regression modeling was used to compute adjusted hazard ratios (HR) with 95% confidence intervals (CI). The median age was 70 years (interquartile range, 60-81). The majority of patients were white (84.7%, n=465), on Medicare (56.5%, n=310), and were treated at an academic treatment facility (63.2%, n=347). History of prior cancer was recorded in 39.3% of patients. The most common treatment modality was RT (43.5%, n=239) followed by CRT (24.6%, n=135), S+R (24.0%, n=134), and S+CRT (7.8%, n=43). Median follow-up in all and surviving patients was 11.9 and 29 months, respectively. A total of 436 deaths were reported, and the overall 3-year survival rate was 23.0% (median survival, 12.6 months). On multivariate analysis, older age, CDS ≥2, advancing T, and N category was associated with poor survival. Patients with a history of cancer (HR 1.40, 95% CI 1.13-1.75, p=0.003) and M1 disease (HR 2.34, 95% CI 1.73-3.15, p<0.0001) also reported poor survival. Compared to RT, improved survival was noted for CRT (HR 0.61, 95% CI 0.47-0.80, p=0.0003) and S+R (HR 0.50, 95% CI 0.37-0.69, p<0.0001) but not S+CRT. A BED10 value of ≥59.5 Gy10 was also associated with improved survival (HR 0.57, 95% CI 0.46-0.71, p<0.0001). No significant difference in survival was noted by race, insurance, income, and treatment facility. Factors adversely affecting survival in HNC patients treated with SBRT included a history of prior cancer, older age, patient co-morbidities, advanced T, N, and M stage. SBRT dose fractionation with a BED10 of ≥59.5 Gy, and combination with chemotherapy and surgery improves survival for HNC.