Study Results Fail to Support Routine Use of Prophylactic Irradiation in Mesothelioma

Routine use of prophylactic radiotherapy in patients with malignant pleural mesothelioma is unnecessary, according to multicenter, open-label, phase 3, randomized controlled trial findings published in the Journal of Clinical Oncology.

To diagnose and treat malignant pleural mesothelioma, patients have to undergo an invasive procedure at the chest wall, which can cause tumor-cell seeding — a form of metastasis where malignant cells are disturbed and spread elsewhere in the body. Therefore, development of a subcutaneous tumor occurs as a chest wall metastasis.

The use of radiation can kill the mesothelioma cells, preventing further tumor growth in previously healthy tissue; however, according to the Mesothelioma and Asbestos Awareness Center, preventing metastasis is imperative because it accounts for approximately 90% of all cancer fatalities.

To minimize and prevent this from occurring, prophylactic radiotherapy delivered to the site of the chest wall procedure has been in use for the past 20 years. However, its use began before the era of chemotherapy and its efficacy is unknown.

“This has resulted in conflicting recommendations in international guidelines and consensus that suitably powered randomized trials are needed,” the researchers wrote. Therefore, they aimed to determine the efficacy of prophylactic radiotherapy in reducing the incidence of chest wall metastases after a procedure in patients with malignant pleural mesothelioma.

After undergoing a chest wall procedure, 186 patients were randomized to receive prophylactic radiotherapy within 42 days of the procedure and 189 underwent no prophylactic radiotherapy.

Incidence of chest wall metastasis within six months from assignment of prophylactic radiotherapy or no prophylactic radiotherapy served as the primary outcome measure.

The researchers saw no difference between patients who did and did not receive prophylactic radiotherapy (six [3.2%] vs. 10 [5.3%] incidences), respectively). Moreover, at one year, there were 15 (8.1%) and 19 (10.1) incidences, respectively.

Overall, there were 46 recorded incidences of chest wall metastasis: 17 in the prophylactic radiotherapy group and 29 in the non-treatment group, and there was no significant difference in the cumulative incidence.

Skin toxicity was the most common side effect associated with prophylactic radiotherapy, including 96 patients (51.6%) with grade 1, 19 patients (10.2%) with grade 2 and one patient with grade 3.

“The results of this study do not support the routine use of prophylactic radiotherapy after a diagnostic or therapeutic chest wall procedure in the era of chemotherapy for patients diagnosed with (malignant pleural mesothelioma),” the researhers wrote. “Our findings confirm that prophylactic radiotherapy should not be considered part of the routine treatment of patients with (malignant pleural mesothelioma) who can be spared the limited but common skin toxicity and the inconvenience of extra hospital visits conferred by this unnecessary practice.”