The Role of Dosimetric Parameters in Radiation Pneumonitis: A Functional Approach in Adjuvant Treatment of Malignant Pleural Mesothelioma

Cancers 2026 January 27 [Link]

Luca Dominici, Davide Franceschini, Mauro Loi, Ruggero Spoto, Antonio Marco Marzo, Beatrice Marini, Mariya Boyanova Ilieva, Nicola Lambri, Francesco La Fauci, Ciro Franzese, Marta Scorsetti

Abstract

Background: Malignant pleural mesothelioma (MPM) is an aggressive neoplasm, the major cause of which is asbestos exposure. Adjuvant radiotherapy after pleurectomy/decortication (P/D) aims at reducing locoregional recurrence but is limited by the risk of radiation pneumonitis (RP). In this study, we attempted to evaluate the predictive value of conventional and functional dosimetric parameters in assessing RP risk.

Methods: This retrospective study analyzed 68 patients with non-metastatic MPM treated with adjuvant radiotherapy after P/D. Dosimetric parameters, including V20, V5, and mean lung dose (MLD), were calculated for both total lung volume and functional lung volume (FLV), with emphysematous regions excluded based on CT imaging thresholds. Statistical analyses assessed correlations between these parameters and acute RP incidence.

Results: Acute RP developed in 42% of patients, and 28% had moderate-to-severe (Grade 2-3) events. V20 and FCL_V20 were significantly associated with the risk of RP (p = 0.017 and p = 0.028, respectively). Predictive accuracy for conventional V20 (AUC = 0.668) and Functional Contralateral Lung V20 (FCL_V20) (AUC = 0.655) showed moderate efficacy, without further significant improvement in using functional parameters. A V20 threshold > 1.8% predicted severe RP with high specificity (89.8%).

Conclusions: While functional lung delineation provides an alternative in dosimetry, conventional V20 is a robust predictor of RP. Optimization of dosimetric constraints, in an effort to reduce pulmonary toxicity in MPM patients, should be further combined with advanced radiotherapy techniques and biomarkers.