ESTRO 2024 - Abstract Book

S1690

Clinical - Lung

ESTRO 2024

The use of Stereotactic Ablative Body Radiotherapy (SABR) to treat central lung tumours is challenging. Toxicity data is limited, and the optimal dose fractionation has not been established. We aimed to collect toxicity and efficacy data from our patients. We believe this is the largest dataset reported to date.

Material/Methods:

We evaluated 248 patients treated between 2019 and 2022 who had central/ultra-central tumours treated with 8 fraction SABR. Patients with primary lung cancer (n=165) and oligometastatic disease (n=83) were included. The median dose was D95 60Gy (37Gy-60Gy). Central lung tumours received D95 50-60Gy. Ultra-central tumours were defined as those in which the ITV is ≤1cm from the trachea, oesophagus or proximal bronchial tree. A risk adapted SABR fractionation with the dose reduced <44Gy is used for ultra-central SABR to minimise toxicity. This protocol is reserved for oligometastatic tumours only (n=38). The mean age was 73.8 years (33.5-92.1). 217 patients had a single site treated and 31 patients had multiple. Median follow-up was 349 days (10-1359).

Results:

141 patients reported toxicity, these were mostly grade 1 and 2. There was 1 account of grade 4 toxicity (bronchial obstruction) and 5 patients experienced grade 3 toxicity; lung infection (n=2), dyspnoea (n=2) and cough (n=1). The risk adapted SABR fractionation used for ultra-central tumours appears well tolerated; 36.8% of patients reported no toxicity, 57.9% grade 1 and 5.3% grade 2. The Kaplan-Meier method was used to determine survival probability; both local and distant disease progression were used for progression free survival (Table 1). Good local control was seen at 2 years in both the central and ultra-central group, with local control rates 96% and 80% respectively.

Table.1 Overall and progression free survival of patients receiving central/ultra-central lung SABR.

Conclusion:

Central and ultra-central SABR can be delivered with acceptable short-term toxicity and efficacy using organ at risk constraints from the SABR consortium guidance. More work is needed to define and corelate toxicity and outcomes with dose fractionation and harmonise constraints internationally. Better online imaging including the potential of the MR-Linac may allow higher doses in this situation whilst retaining acceptable doses to OAR.

Keywords: Central SABR, Efficacy, Toxicity

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