No abstract

Background: For patients with early stage or medically inoperable lung cancer, stereotactic body radiotherapy (SBRT) is a general accepted and effective treatment option. While most successful data come from peripherally located tumours, the role of SBRT in ultra-central tumours remains controversial. The aim of this single-center cohort study was to evaluate the safety and efficacy of protracted SBRT with 60 Gy in 12 fractions (with a biological effective dose (BED 10 ) of 90 Gy) for patients with ultra-central lung tumours. Methods: All patients with ultra-central lung tumours treated in our institution with 60 Gy in 12 fractions from January 2012 until April 2020 were included. Ultra-central tumours were defined as planning target volume (PTV) abutting or overlapping the main bronchi, trachea and/or oesophagus. Data regarding patient-, tumour-, and treatment-related characteristics were extracted from the institutional database. All patients were treated as per institutional protocol following International Commission on Radiation Units and Measurements (ICRU) guidelines. Results: A total of 72 patients met the criteria for ultra-central tumour location. The PTV abutted the main bronchus, trachea or oesophagus in 78%, 21% and 21% of cases, respectively. At a median follow-up of 19 months, 1-and 2-years local failure-free survival rates were 98% and 85%, respectively. Overall survival rates at 1 and 2 years were 80% and 52% respectively. Grade 3 or higher toxicity was observed in 21%, of which 10 patients (14% of total) died of lung haemorrhage after a median time of 11 months. A significant difference between patients with or without ≥ grade 3 toxicity was found for the mean dose (D mean ) to the main bronchus ( p = 0.015), where a D mean BED 3 of ≥ 90 Gy increased the risk of ≥ grade 3 toxicity significantly. Conclusions: A protracted SBRT regimen of 60 Gy in 12 fractions for ultra-central lung tumours leads to high local control rates with acceptable toxicity, albeit at the risk of serious toxicity and even mortality. Therefore, possible risk factors of lung hemorrhage such as dose to the main bronchus, peri-or endobronchial tumour location and anti-vascular endothelial growth factor (anti-VEGF) or antithrombotic therapy should be taken into account.Legal entity responsible for the study: University Medical Center Utrecht. Funding: Has not received any funding. Disclosure: All authors have declared no conflicts of interest.Background: SBRT is the standard treatment for early-stage NSCLC patients that are medically unfit for surgery and is associated with excellent results in terms of local control. However, approximately 30% of patients develop distant metastases over time. Adjuvant chemotherapy is rarely administered because of a lack of data and the fragility of