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Ultra-central (UC) lung tumors are defined as those abutting the proximal bronchial trees. Stereotactic body radiation therapy (SBRT) for UC tumors is difficult due to concerns about serious toxicities. Therefore, we report safety and efficacy of moderate-intensity SBRT for UC tumors in our institution.

Patients with UC tumors underwent SBRT at a dose of 45 to 60 Gy in 10 fractions, with Dmax in the target volume not exceeding 110% of the prescribed dose. The primary outcomes were tumor response and overall survival (OS).

From January 2017 to May 2021, we treated twenty patients who had been treated with UC tumors. The median follow-up time was 15.8 months (range: 2.7–53.8). Ten of the 20 patients (50.0%) showed a complete response (CR), five (25.0%) had a partial response (PR), two (10.0%) had stable disease (SD) and three (15.0%) showed progressive disease (PD); the response and disease control rates were 75.0% and 90.0%, respectively. PD patients showed local progression at median 8.3 months (range: 6.8-19.1) after SBRT. Fourteen patients were alive with no evidence of disease or with controlled disease until the last follow-ups. One-year, 2-year OS rate was 79.1% and 63.9%, respectively. Five patients died due to a non-RT cause. One patient experienced massive hemoptysis 6 months after SBRT, which resulted in death. One patient experienced grade 2 esophageal pain and another had grade 1 cough. Otherwise, no grade 3 or higher toxicities were reported.

Moderate-intensity SBRT might aid in achieving good control of UC tumors. SBRT is well-tolerated treatment modality for UC tumors. Future studies are warranted due to a small number of patients and short period of follow-up.