Thirteen patients with early glottic cancer were enrolled for a phase 1 dose escalation trial of stereotactic ablative radiation therapy. Doselimiting toxicities, specifically grade 3 late toxicities, occurred in 2 of 6 patients who received 55 Gy in 11 fractions. Hypofractionated radiation therapy at doses of 59.5 Gy in 17 fractions was well tolerated with acceptable voice outcomes, quality of life, and local control. Purpose: The early results of a phase 1 study of stereotactic ablative radiation therapy for early-stage glottis cancer were previously reported. However, additional late adverse events occurred in the second arm during the follow-up period. In this study, the dose-limiting toxicities and premature closure of the clinical trial are reported. Methods and Materials: Thirteen patients with cT1-2N0M0 squamous cell carcinoma of the glottis were enrolled between May 2015 and July 2018. Seven patients in the first arm received 59.5 Gy to the gross tumor volume and 47.6 Gy to the remaining larynx, delivered in 17 fractions. The second arm dose was 55 Gy and 40.7 Gy in 11 fractions to the gross tumor volume and the remaining larynx, respectively. Patients were treated according to the simultaneous integrated boost approach with volumetric modulated arc therapy. Results: The median follow-up was 37 months (range, 6-41.4) for the first arm and 14.5 months (range, 4.8-21.5) for the second arm. Maximum acute toxicity was grade 2 laryngeal mucositis for each arm. Maximum chronic toxicity was grade 3 laryngeal inflammation, occurring in 2 patients (33.3%) in the second arm. One patient underwent a laryngomicrosurgical biopsy for a vocal cord ulcer, and another patient underwent supraglottic laryngectomy because of arytenoid cartilage necrosis. In the first
Due to more light scattering and effective thermal confinement, 532 nm induced more efficient tissue ablation with a smaller coagulative necrotic zone. Comparable ablation depth may enable a potential tissue incision technique with 532 nm, possibly allowing both tissue removal and biopsy intraoperatively.
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