Malignant pleural mesothelioma is a devastating cancer, with survival rates ranging from as low as 17% to 46%. Diagnosis and/or treatment usually involves an invasive chest wall procedure, however, this carries the risk of tumor-cell seeding at the site of the procedure and subsequent development of metastases. Due to this risk, prophylactic radiotherapy is commonly delivered to the site of the chest wall procedure. However, past studies assessing the efficacy and safety of this approach have been underpowered and have produced conflicting results. In this randomized controlled trial, 375 patients with malignant pleural mesothelioma (MPM) were assigned to receive prophylactic radiotherapy or no prophylactic radiotherapy after a diagnostic or therapeutic chest wall procedure to study the impact on incidence of metastases on the ipsilateral chest wall (chest wall metastases, CWM) 6 months after randomization. There was a similar proportion of patients receiving chemotherapy in the two groups (66.7% in the prophylactic radiotherapy group, 60.3% in the no-radiotherapy group). Researchers found that there was no difference in the proportion of CWM 6 months after randomization between the two groups (3.2% in the prophylactic radiotherapy group vs. 5.3% in the no-radiotherapy group, OR 0.60, 95% CI 0.17 to 1.86, p=0.44). There was also no difference at 12 months (8.1% vs. 10.1%, respectively, OR 0.79, 95% CI 0.36 to 1.69, p=0.59). Skin toxicity was the most common radiotherapy-related adverse event, and occurred in 116 of 186 patients in the prophylactic radiotherapy group. A limitation of this study was the absence of blinding of the participants and investigators. In summary, results from this study do not support the routine use of prophylactic radiotherapy after a chest wall procedure in patients with malignant pleural mesothelioma.
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