Practical Radiation Oncology 2019 January 14 [Link]
Thompson MR1, Dumane VA1, Lazarev SA1, Zia Y2, Rosenzweig KE3
We aimed to determine dose-volume constraints that correlate with severe (grade ≥3) radiation pneumonitis (RP) in patients diagnosed with malignant pleural mesothelioma (MPM), treated using volumetric modulated arc therapy (VMAT).
Data from 40 patients with MPM who underwent pleurectomy decortication (P/D) and adjuvant radiation therapy at our institution between December 2010 and October 2016 were retrospectively analyzed. Dosimetric variables for the absolute volume as well as percentage volume of the ipsilateral lung, contralateral lung and heart were recorded. Events of RP were assessed using the Common Terminology Criteria for Toxicity and Adverse Events v4.0. Statistical analysis with Wilcoxon rank-sum, Spearman rank correlation and Receiver operating characteristic curves was computed using MATLAB V9.1, RV3.4 and SAS V9.4.
Of 40 patients, 26 patients were male (65%). The median age at diagnosis was 66.5 years (range 44-84). The median prescription dose was 45 Gy (30 Gy – 54 Gy). Five patients (12.5%) had grade ≥ 3 RP. Incidence of grade ≥ 3 RP showed significant correlation (P < 0.05) with the absolute volume and percentage volume of the ipsilateral lung spared of 20 Gy and higher (55cc; 7%) as well as spared of 30 Gy and higher (200cc; 23%). Dosimetric variables of the contralateral lung, total lung and heart did not show correlation with incidence of grade ≥ 3 RP.
In our cohort, sparing ipsilateral lung of at least 55cc of 20Gy and 200cc of 30Gy correlated with a reduced incidence of severe (grade ≥3) radiation pneumonitis.