Dosimetric Correlates of Pulmonary Toxicity in Patients with Malignant Pleural Mesothelioma Receiving Radiation Therapy to the Intact Lungs.

PURPOSE

We aimed to determine dose-volume constraints that correlate with severe (grade ≥3) radiation pneumonitis (RP) in patients diagnosed with malignant pleural mesothelioma, treated using volumetric modulated arc therapy.

METHODS AND MATERIALS

Data from 40 patients with malignant pleural mesothelioma who underwent pleurectomy decortication and adjuvant radiation therapy at our institution between December 2010 and October 2016 were retrospectively analyzed. Dosimetric variables for the absolute volume and 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, version 4.0. The 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.

RESULTS

Of the 40 patients, 26 patients (65%) were male. The median age at the time of diagnosis was 66.5 years (range, 44-84 years). The median prescription dose was 45 Gy (range, 30-54 Gy). Five patients (12.5%) had grade ≥3 RP. The incidence of grade≥ 3 RP showed a significant correlation (P < .05) with the absolute volume and percentage volume of the ipsilateral lung spared of ≥20 Gy (55 cc; 7%) and spared of ≥30 Gy (200 cc; 23%). Dosimetric variables of the contralateral lung, total lung, and heart did not show a correlation with incidence of grade ≥3 RP.

CONCLUSIONS

In our cohort, sparing the ipsilateral lung of at least 55 cc of 20 Gy and 200 cc of 30 Gy correlated with a reduced incidence of severe (grade ≥3) RP.