Phase 1 Fractional Dose-Escalation Study of Equipotent Stereotactic Radiation Therapy Regimens for Early-Stage Glottic Larynx Cancer

Purpose Early-stage glottic larynx squamous cell carcinoma (GLC) is a relatively common disease with excellent oncologic control, but treatment is associated with acute dysphagia and long-term voice quality changes. This phase 1 study of hypofractionated radiation therapy for early-stage GLC increased the fraction size while reducing the number of fractions until 5-fraction stereotactic ablative radiation therapy (SABR) was delivered. Methods and Materials Eligible patients had received a diagnosis of stage Tis to T2 GLC. Patients who had undergone prior curative-intent surgery were excluded. The equipotent dose levels were as follows: (1) level 0, 50 Gy in 15 fractions (n = 4); (2) level 1, 45 Gy in 10 fractions (n = 13); and (3) level 2, 42.5 Gy in 5 fractions (SABR level, n = 12). Grade 3 or 4 laryngeal edema, voice, dyspnea, stridor, or cough were the predefined dose-limiting toxicities. Results Twenty-nine patients were enrolled from November 2013 to March 2017. The median and minimum follow-up times were 39.2 and 13 months, respectively. Two actively smoking patients, 1 treated in level 1 (grade 4 laryngeal edema, grade 3 dysphagia) and 1 treated in level 2 (grade 3 laryngeal necrosis, dysphagia), developed dose-limiting toxicities. The former patient soon developed a local recurrence, and the latter patient recovered. There were a total of 5 local recurrences: 2 in level 0 and 3 in level 1. The Voice Handicap Index results showed robust long-term voice quality with median values of 7 and 0 at 6 and 12 months, respectively. Conclusions Given the tolerability, excellent voice outcomes, and preliminary efficacy data of 5-fraction glottic larynx SABR, this regimen warrants further study.