Treating patients with high-dose radiotherapy after chemotherapy and surgery for malignant pleural mesothelioma does not achieve improvements in local relapse and overall survival, according to data from a prospective randomized phase II trial presented at the European Society for Medical Oncology (ESMO) 2014 Congress in Madrid, Spain.

“Mesothelioma remains a difficult disease to find better treatment options for, so we asked whether high-dose hemithoracic radiotherapy would decrease the rate or delay the time of local recurrence after chemotherapy and radical surgery,” said lead author Rolf A. Stahel, MD, from the Clinic and Policlinic for Oncology, at the University Hospital Zurich, Switzerland, and current President of ESMO.

The multicenter trial included 153 patients with surgically treatable malignant pleural mesothelioma, who were first treated with three chemotherapy cycles of cisplatin and pemetrexed, followed by surgical removal of affected lung tissue, with the goal of complete removal of the cancerous areas of lung.

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In a second part of the study, researchers randomly assigned 54 patients to receive either radiotherapy or no further treatment, with the primary end point being the duration of relapse-free survival.

Although preliminary evidence had suggested that the addition of radiotherapy might improve outcomes, the study failed to find any differences in relapse-free survival between patients treated with the additional radiotherapy and those who were not.

Stahel said researchers were hoping for a more positive signal from the study. “We aimed for a 6 month delay in local recurrence, which would be meaningful because it’s an aggressive treatment for patients.”

In summary, Stahel said, “It demonstrates that, as in other solid tumors, when two modalities are not sufficient it’s very rare that the third modality added would make a benefit.”

The multimodality approach of chemotherapy followed by major surgery and irradiation of high volumes of the chest is one of the accepted treatments in very fit patients. However, it is a combination associated with high morbidity, commented Paul Baas, MD, PhD, from the Department of Thoracic Oncology, The Netherlands Cancer Institute, Amsterdam.

“The study by Stahel [and colleagues] indicates that the contribution of radiation does not improve time to recurrence of the disease,” said Baas. However, he also stressed that the results did not lead him to conclude that there was no role for adjuvant radiation in this setting, pointing out that this was a phase II trial, and therefore not necessarily the final conclusion, and that selection of patients with differing pathology, stage, and performance could influence outcome.