Malignant pleural mesothelioma (MPM) is a tumour that originates from the pleural layers (visceral and parietal) that envelop the lungs and the inner wall of the thoracic cage. In other tumour contexts, numerous studies have demonstrated a synergistic effect between RT and Immune Checkpoint Inhibitors (ICIs), mainly due to immunogenic effects attributed to high doses of RT and ICIs-mediated activation of anti-tumour T lymphocytes. Both treatments, RT and immunotherapy, have demonstrated a survival advantage in MPM, but are associated with non-negligible pulmonary toxicity. Therefore, the combination of these 2 therapeutic approaches requires a careful assessment of risk factors for the occurrence of toxicity. The identification of circulating biomarkers capable of predicting the onset of severe toxicity induced by radical radiation treatment is an important clinical need in MPM. This study aims to monitor circulating biomarkers, such as molecules involved in inflammation and oxidative stress and cellular effectors modulated by radiation treatment and potentially associated with the development of toxicity and/or markers of an immunogenic effect of radiotherapy in the peripheral blood of subjects with malignant pleural mesothelioma for treatment with radical hemithoracic radiotherapy.