Abstract
BACKGROUND: Pharyngeal mucositis and esophagitis incidence following re-irradiation stereotactic body radiotherapy (SBRT) for spinal metastases remains unclear. We retrospectively examined their incidence and risk factors after re-irradiation SBRT to clarify organ tolerance. METHODS AND MATERIALS: Patients who underwent spine SBRT following prior conventional radiotherapy were included if the SBRT delivered more than 10 Gy to the pharynx or esophagus. SBRT dose was limited to 24 Gy in two fractions. Dose constraints were pharyngeal D(1 cc) < 20, esophageal D(2.5 cc) < 19, and D(0.035 cc) < 24 Gy. The primary endpoint was pharyngeal mucositis and esophagitis occurrence. Patient demographics, clinical factors, and dose-volume parameters were analyzed as predictors of symptomatic toxicities. RESULTS: Ninety-three patients were included (60 males; median age, 66 years). The median follow-up was 15 (range: 3-111) months. One patient with grade 3 toxicity (1 %) was observed, with no grade 4-5 toxicities. Grade 1 (symptomatic) pharyngeal mucositis occurred in 58 % (14/24) of patients, and grade 2 esophagitis occurred in 27 % (23/85). Clinical factors and symptomatic toxicities were not significantly associated. The estimated D(max) values corresponding to a 20 % risk of symptomatic toxicity were 16.6 Gy for the pharynx and 22.8 Gy for the esophagus. CONCLUSIONS: Grade ≥ 3 pharyngeal mucositis and esophagitis were rare; the current dose constraints are safe for re-irradiated spine SBRT. Reducing the pharyngeal and esophageal maximum doses may be helpful among patients for whom avoiding symptomatic mucositis is particularly important.