Reduction of the acute pulmonary toxicity with a VMAT adaptive radiotherapy in lung cancer patients
Vincent Bourbonne,
France
PO-1270
Abstract
Reduction of the acute pulmonary toxicity with a VMAT adaptive radiotherapy in lung cancer patients
Authors: Vincent Bourbonne1,2, François Lucia1,2, Vincent Jaouen2,3, Julien Bert2, Martin Rehn1, Olivier Pradier1,2, Dimitris Visvikis2, Ulrike Schick1,2
1University Hospital, Radiation Oncology, Brest, France; 2Université de Bretagne Occidentale, LaTIM, UMR 1101 INSERM, Brest, France; 3Institut Mines, Télécom Atlantique, Brest, France
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Purpose or Objective
In patients treated with radiotherapy for a locally advanced lung cancer, respect of dose constraints to organs at risks (OARs) insufficiently protects patients from acute pulmonary toxicity (APT), such toxicities being associated with a potential impact on treatment’s delivery and the patients’ quality of life. Daily dosimetric planning does not take into account regional lung functionality. An APT prediction model combining usual dosimetry features with the mean dose (DMeanPmap) received by a voxel-based volume (Pmap) localized in the posterior right lung has been previously developed. A DMeanPmap > 30.3Gy was associated with a higher risk of APT. In this study, the authors aim to demonstrate the possibility of decreasing the DMeanPmap via a VMAT-based adapted planning and evaluate the consequences on the risk of APT.
Material and Methods
Among the 207 patients included in the initial study, only patients that presented with a APT ≥ grade 2 and with a probability of APT (ProbAPT ≥ 8%) based on the prediction model were included. Dosimety planning was optimized with new constraints on the Pmap region. Initial and optimized treatment plans were compared using the T-test for independent variables and the non-parametric Mann-Whitney U test otherwise, regarding both doses to OARs and PTV coverage (Planning Target Volume). Conformity and heterogeneity indexes were also compared.
Results
Dosimetric optimization was considered successful for 27 out of the 44 included patients (61.4%), meaning the dosimetric constraint on the Pmap region was achieved without compromising the PTV coverage (p = 0.61). Overall, optimization significantly decreased median DMeanPmap from 28.8Gy (IC95% 24.2-33.4) to 22.1Gy (IC95% 18.3-26.0). When focusing on the predicted risk of APT inputting the new dosimetric features, optimization significantly reduced the risk of APT (p < 0.0001) by reclassifying 43.2% (19/44) of the patients.
Conclusion
Our approach appears as both easily implementable on a daily basis and efficient at reducing the risk of APT. Regional radiosensitivity should be considered in usual lung dose constraints, opening the possibility of an easily implementable adaptive dosimetry planning.