Normal Tissue Dose Constraints for Multiple Lung Stereotactic Radiotherapy Treatments

Normal Tissue Dose Constraints for Multiple Lung Stereotactic Radiotherapy Treatments

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Corresponding Author
Beshar Allos
Department of Clinical Oncology, Cancer Centre, Queen Elizabeth Hospital Birmingham, Mindelsohn Way, Edgbaston, Birmingham, UK

A B S T R A C T

Introduction: The role and use of stereotactic radiotherapy (SABR) is evolving rapidly. A key article by Hanna et al. (2017) provides an excellent overview of current evidence and suggestion of sensible dose constraints. Given the topical nature of this discussion we present a short retrospective analysis of treating multiple lung SABR patients at our centre. Method: We retrospectively analysed toxicity, both early (within 3 months of SABR) and late, and normal tissue dose constraints on all patients who had multiple lung lesions treated with SABR (using volumetric modulated arc therapy (VMAT) technique) at our tertiary centre over a 25-month period from April 2016 until May 2018. Results: We have treated 78 lung lesions in 37 patients with a combination of synchronous lung cancer primaries and lung metastases diagnoses. Median follow-up was 9 months. Almost all patients received treatment on the same day for multiple lesions. We report no grade 3 toxicities in any patient nor any unexpected side effects. 5 patients (14.7%) developed grade 2 pneumonitis. In all 5 patients, lung V12.5 was >20% (range 20.8-32.2%), yet only 1 patient exceeded acceptable lung V20 constraints. Regarding long-term toxicity, 66.6% of patients reported no treatment-related effects. Of 9 patients with long-term toxicity, 8 exceeded V12.5 constraint of <15%, indeed of these 5 were >20%. Lung V20 levels were acceptable for the majority of these. Local control of treated lesions at median follow-up in all comers was 86.2%. Discussion: Our findings show that multiple lung SABR is tolerable, safe with minimal long-term toxicity and acceptable early toxicity. Defining normal lung V12.5 of <15% (optimal) and <20% (acceptable) will significantly reduce the risk of pneumonitis and longer-term toxicity, proving itself more predictive than lung V20 levels for toxicity. Additionally, treating multiple lesions concurrently appears to bare no extra risk to patients.

Article Info

Article Type
Research Article
Publication history
Received: Wed 27, May 2020
Accepted: Mon 15, Jun 2020
Published: Wed 24, Jun 2020
Copyright
© 2023 Beshar Allos. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. Hosting by Science Repository.
DOI: 10.31487/j.COR.2020.06.17