Stereotactic Body Radiation Therapy (SBRT) for Head and Neck Cancer Re-Irradiation: Should >180˚ Carotid Encasement or Dermal Involvement Remain an Exclusion Criteria?

Abstract

Patients with recurrent head and neck cancer (HNC) who present with carotid encasement (CE) >180˚ and skin involvement/abutment (SI/A) are often not considered for SBRT re-irradiation and are excluded from RTOG 3507. We reviewed our institutional experience of SBRT re-irradiation in such cases. From an IRB approved registry, we identified previously irradiated HNC patients treated by SBRT with CE >180˚, SI/A, or use of bolus from 2013-2022. Toxicity as per CTCAEv4.0 and recurrence patterns were analyzed. The cumulative incidence of local progression was estimated with death as a competing risk. Survival analysis was performed with the Kaplan-Meier method. Thirty-five patients were treated with SBRT to 37 sites with median follow up of 5.7 months (mo) (IQR 2.7-10.6). A total of 20 cases exhibited CE >180˚, 20 cases had SI/A, and 3 cases had both. The median time from prior radiation was 12.7 mo (range 1.9-144.1). Histology was squamous cell carcinoma in 89%. The site of SBRT was most commonly the neck (65%), 24% mucosa, 8% skull base, and 3% scalp. SBRT was delivered in 5 fractions every other day (62%) or 2 fractions per week (38%). 78% (N = 29) received ≥40 Gy while 22% (N = 8) received a lower dose. The cumulative incidence of local failure at 3 and 6 mo was 12.4% (95% CI 0.8-24.0) and 31.3% (95% CI 14.9-47.8), respectively. The median time of local and regional recurrence free survival was 7.0 and 4.9 mo. Median OS was 8.3 mo. Of the 20 cases with true SI, 40% (N = 8) completely resolved, 35% (N = 7) improved or had residual ulceration attributed to disease, and 25% (N = 5) had ulceration related to toxicity. There were no carotid bleeding events (CBE) related to SBRT, however 10% (N = 2) experienced fatal CBE related to progressive disease at 2.3 mo and 6.7 mo from SBRT. The rate of grade ≥2 treatment related skin toxicity was 19% (N = 7) and only occurred in those with pre-SBRT SI/A. These included a grade 2 neck wound and tracheostomy infection, a grade 3 infection, and two grade 3 soft tissue necrosis. One patient had cellulitis/meningitis related to scalp radiation, and one had an untreated SBRT wound as they transitioned to hospice. Dysphagia requiring PEG occurred in 5% (N = 2), one of which was related to CNX palsy. Six patients (17%) had post-SBRT nerve impairment including one each of grade 2 facial nerve paralysis, grade 2 brachial plexopathy, grade 3 CNVIII dysfunction, grade 3 CNX impairment, and two patients with grade 2 CNXII impairment. SBRT for locally recurrent previously radiated HNC can provide effective local control in a patient population at high risk of morbidity and mortality from local disease progression. In patients who have >180˚ CE or SI/A, we observed non-trivial toxicity, but disease progression may have been more morbid. For appropriately counseled patients with limited treatment options, CE or SI/A may not be an absolute contraindication to SBRT re-irradiation.