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.