Stereotactic Body Radiation Therapy (SBRT) Following Salvage Surgery for Previously Irradiated Head and Neck Cancer

Abstract

<h3>Purpose/Objective(s)</h3> Per the National Comprehensive Cancer Network (NCCN) guidelines, patients with locoregional recurrence or second primary with prior radiation therapy have a "dealer's choice" array of options following salvage resection for head and neck cancer (HNC). One option is stereotactic radiation therapy (SBRT). The aim of this retrospective study was to evaluate this shorter course of postoperative radiation therapy for patients in a previously irradiated area of the head and neck. <h3>Materials/Methods</h3> We analyzed the outcomes of patients treated with SBRT following resection of a recurrent or second primary head and neck cancer between 2015-2021 at our institution. Outcomes of interest included local control (LC), regional control (RC), distant metastatic control (DMC), overall survival (OS) and toxicity. Cox proportional hazards were used to identify predictors of OS. Follow up interval was defined as from the end of SBRT to last follow up or death. <h3>Results</h3> Sixty-seven patients with 71 resected lesions formed the cohort. Fifty-five percent of cases (n=39) were squamous cell carcinoma (SCC). The median initial radiation to reirradiation (XRT- reXRT) interval was 37 months (range 4-285), and the median interval from surgery to SBRT was 6.9 weeks (range 3.9-13.9). Twenty-eight percent (n=20) of patients received induction systemic therapy, 27% (n=19) received concurrent and 17% (n=12) received adjuvant therapy. The median SBRT dose was 35Gy (range 10-45Gy) delivered in 5 fractions (range 1-6) at median BED of 59.5Gy (range 20-84.8Gy) to a median target volume of 21cc (range 1-266cc). Median follow up was 11 months (range 0-50). Median LC was 38 months with 14 in-field failures and 5 marginal failures. The 1-year LC was 73%, 1-year RC was 70%, 1-year DMC was 80% and 1-year OS was 81%. On multivariate analysis, SCC histology was associated with worse OS (HR 4.48, 95% CI 1.33-15.12, p=0.02) and longer XRT- reXRT interval was associated with improved OS (HR 0.99, 95% CI 0.97-0.99, p=0.03). There was 1 grade 3 acute toxicity requiring feeding tube placement and no grade 4+ acute toxicities. With respect to late toxicities, there were 12 grade 3 (2 xerostomia, 1 pain, 3 soft tissue infection/necrosis, 1 trismus, 1 hearing loss, 1 osteoradionecrosis (ORN), 3 dysphagia requiring feeding tube), 2 grade 4 (1 ORN, 1 temporal lobe necrosis) and 1 grade 5 toxicity associated with complications from temporal lobe necrosis. <h3>Conclusion</h3> Oncologic and toxicity outcomes suggest that surgery and SBRT re-irradiation may be an appropriate option for well selected patients in this setting. The role and sequence of systemic therapy requires further investigation and reduced exposure to normal structures may further decrease late toxicities.