Stereotactic Radiation Therapy in 3 Fractions for T1 Glottic Cancer.

Purpose/objective(s): To report the results of a phases 1 and 2 study on stereotactic body radiation therapy (SBRT) for early glottic cancer.

Methods and materials: This a prospective study at a single institution enrolling patients with T1 glottic cancer. The true vocal cords (TVCs) were divided into thirds and the third(s) containing disease prescribed 36 Gy in 3 fractions. The portions of the TVCs next to the involved one were planned to receive 30 Gy in 3 fxs. SBRT was delivered by a linear accelerator-based approach using multiple arcs. Toxicity was scored by Common Terminology Criteria for Adverse Events and late events were considered those occurring 3 months after SBRT. Voice quality was investigated by the Voice Handicap Index at regular intervals. The planned sample size was 75 patients.

Results: Accrual was discontinued after 33 patients because of concerns for late toxicity. T stage was as follows: T1a: 23 patients (69.7%); T1b: 10 patients (30.3%). All patients received the planned treatment and the median follow-up time was 51.5 months (IQR, 47.9-61.0 months). At last follow-up, all patients were alive and without evidence of disease but 2 patients who died for intercurrent causes. The local control rate was 100% at 4 years. Six patients (18.2%) developed soft tissue necrosis (N = 4) or cartilage necrosis (N = 2) after a median time of 14.9 months from SBRT. Five out of 6 necrotic events were observed in patients who kept smoking and/or had a recent COVID infection. All 4 soft tissue events healed with conservative therapy. After an initial deterioration, the average Voice Handicap Index score significantly improved at 6 months over baseline.

Conclusions: SBRT to 36 Gy in 3 fractions is highly effective in controlling T1 TVC carcinoma, but necrosis, although mostly transient, is a concern. On the basis of the present results, a reduction in total dose and a more accurate patient selection are warranted.