Thirteen Years’ Experience of Stereotactic Body Radiation Therapy for Ultra-Central Lung Tumours in Hong Kong

Introduction: Stereotactic body radiation therapy (SBRT) for ultra-central lung tumours is controversial given the proximity of the tumours to critical organs at risk (OARs).We undertook a retrospective review of the efficacy and safety outcomes of ultra-central lung SBRT at a major cancer centre in Hong Kong.Methods: We analysed patients with either primary or oligometastatic ultra-central lung tumours treated with SBRT from 2009 to 2022.The primary outcome was local progression-free survival.Secondary outcomes included the incidence of grade 2 SBRT-related toxicity and overall survival (OS).Clinical and dosimetric factors were collected and analysed for potential associations with survival outcomes.Results: A total of 66 patients were included.Twenty-four cases were primary lung tumours and 42 were lung metastases, with the majority of metastatic lesions being of lung origin (n = 32).Indications for SBRT for lung metastases included oligoprogression (n = 23), oligoresidual disease (n = 13), and oligorecurrence (n = 6).Most patients (86%) received 50 Gy in five fractions.Median follow-up was 54 months, and median OS was 59 months.The 1-year and 3-year local failure-free survival rates were 98% and 88%, respectively.Grade 3 and grade 5 toxicity rates were 4.5% and 6%, respectively.A higher dose to 4 cc of the proximal bronchial tree and tumours located within 1 cm of the mainstem bronchus were associated with grade 2 airway toxicity.Oesophageal mean and maximum doses, and dose to 5 cc of the oesophagus were positively associated with grade 2 oesophageal toxicity.Conclusion: We demonstrated high rates of local control and acceptable toxicity outcomes with ultra-central lung SBRT.Further results from prospective studies may clarify the optimal dose fractionation and OAR constraints for this population.