Stereotactic Radiotherapy in 3 fractions for T1 Glottic Cancer: SBRT in 3 fractions for early glottic cancer.

Abstract

Purpose/objective(s): To report the results of a phase I-II study on SBRT for early glottic cancer.

Materials/methods: This a prospective study at a single Institution enrolling patients with T1 glottic cancer. The true vocal cords (TVC) 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 LINAC-based approach using multiple arcs. Toxicity was scored by CTCAE and late events were considered those occurring 3 months after SBRT. Voice quality was investigated by the voice handicap index (VHI) at regular intervals. The planned sample size was 75 patients.

Results: Accrual was discontinued after 33 patients due to concerns for late toxicity. T stage was as follows: T1a: 23 pts (69.7%); T1b: 10 pts (30.3%). All patients received the planned treatment and the median follow-up time is 51.5 months (IQR: 47.9-61.0 months). At last follow up, all patients are alive and without evidence of disease but two patients who died for intercurrent causes. The local control rate is 100% at 4 yrs. 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 VHI score significantly improved at 6 months over baseline.

Conclusion: SBRT to 36 Gy in 3 fractions is highly effective in controlling T1 TVC carcinoma, but necrosis, though mostly transient, is a concern. Based on the present results, a reduction in total dose as well as a more accurate patient selection are warranted.