The impact of intra-thoracic anatomical changes upon the delivery of lung stereotactic ablative radiotherapy
van Herk, Marcel
AffiliationRadiotherapy Research Group, The Christie NHS Foundation Trust, Manchester,
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AbstractIntroduction: Current evidence demonstrates that 72% of lung patients undergoing curative radiotherapy develop intra-thoracic anatomical changes (ITACs). However, only 12% of these are significant enough to alter treatment dosimetry. The impact of ITACs on patients receiving stereotactic ablative radiotherapy (SABR) for lung cancer, however, is unknown. The aim of this study is to describe the occurrence of ITACs on cone-beam CT (CBCT) imaging and the impact in lung cancer patients treated with SABR. Methods: 100 patients treated with SABR for early non-small cell lung cancer at The Christie Hospital and Leeds Cancer Centre were identified. CBCTs (acquired at every treatment fraction) were reviewed for the presence of the following ITACs: atelectasis, infiltrative change, pleural effusion, baseline shift, gross tumour volume (GTV) increase and GTV decrease. These were graded using a traffic light protocol (developed by Kwint et al., 2014) to assess the potential for target under-coverage. The frequency of physics or clinician requests to review the impact of ITACs was also recorded. Results: Results are shown in Fig. 1. The majority of CBCTs demonstrated no ITACs (85%). However, 18% of ITACs were graded as 'red', implying a potential risk of target under-coverage due to the impact upon the planning target volume (PTV). Most (49%) were 'yellow' with minimal impact upon PTV coverage of the target. Physics or clinician review was required for 9% of treatment fractions. Three patients needed to have their treatment replanned Conclusion: ITACs were observed in 23% of patients undergoing SABR for lung cancer at two independent UK centres. The majority are minor; however, they are associated with unplanned physics or clinician review in 9% of treatments and therefore represent a resource burden. There is a need to incorporate detailed guidance on the management of ITACs into IGRT workflows. This would improve radiographer confidence in treating these patients.
CitationBrown S, Beasley M, Chuter R, Faivre-Finn C, Franks K, Henry A, et al. The impact of intra-thoracic anatomical changes upon the delivery of lung stereotactic ablative radiotherapy. Lung Cancer. 2019;127:S74-S5.
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