Radical hemithoracic radiotherapy doubles survival among certain patients with mesothelioma

Patients with malignant pleural mesothelioma who underwent nonradical surgery and chemotherapy appeared twice as likely to achieve 2-year OS with radical hemithoracic radiotherapy vs. palliative radiotherapy, according to randomized phase 3 study results presented at European Society for Radiotherapy and Oncology Congress.

Based on these findings, the researchers recommended consideration of radical hemithoracic radiotherapy — which also demonstrated acceptable toxicity — as the new standard of care for these patients.

“Patients with mesothelioma are sometimes given radiotherapy to help control their symptoms,” Marco Trovo, MD, chief of the radiation oncology department at University Hospital of Udine in Italy, said in a press release. “However, radiotherapy has evolved dramatically in the last few years, so we wanted to see if it could now be used to prevent the cancer from spreading to nearby tissue, hopefully bringing improvements in survival.”

Trovo and colleagues evaluated 108 patients treated between 2014 and 2018 at the National Cancer Institute of Aviano, Italy. Participants had received nonradical lung-sparing surgery and platinum-pemetrexed chemotherapy. Researchers based eligibility upon factors including PET staging, presence of gross residual disease after surgery, and technical possibility of high-dose hemithoracic radiotherapy delivery. Contralateral mediastinal lymph node metastasis and intrascissural disease served as exclusion criteria.

Researchers stratified patients by histology (epithelioid vs. nonepithelioid), performance status (0-1 vs. 2), surgery (extended pleurectomy/decortication vs. simple pleurectomy/decortication or biopsy only) and stage (I-II vs. III-IVA).

The investigators randomly assigned participants 1:1 to either of the following: radiotherapy to the full hemithorax, not including the intact lung, at a total dose of 50 Gy in 25 fractions, with an extra 60 Gy boost to sections of gross disease; or palliative radiotherapy to thoracotomy scars or gross disease only at a total dose of 20 to 30 Gy in five to 10 fractions.

The study’s objective was to achieve improvement in 2-year OS of 25 percentage points (20% vs. 45%) in the radical hemithoracic radiotherapy group (power 80%; 2-sided alpha error = .05).

Median follow-up was 12.3 months.

The intention-treat-analysis showed that after 64 events, 2-year OS reached 58% in the radical hemithoracic radiotherapy group vs. 28% in the palliative radiotherapy group (P = .003).

Multivariable analysis revealed factors associated with increased survival included radical hemithoracic radiotherapy (HR = 0.46) and epithelioid histology (HR = 0.33).
Researchers noted the following significant toxicities in the radical hemithoracic radiotherapy group: grade 5 pneumonitis (n = 1); grade 3 pneumonitis (n = 4); pulmonary embolism (n = 4); pericardial effusion (n = 2); rib fractures (n = 2); grade 3 erithema (n = 1); grade 3 esophagitis (n = 1); and grade 3 gamma-glutamyl transferase increase (n = 3). Four patients required oxygen for late respiratory failure.

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“This research shows a clear survival benefit in using this type of radiotherapy for patients [with mesothelioma] whose tumors can only partially be removed by surgery,” Trovo said. “We believe that this should be considered the new standard of care for these patients.” – by Jennifer Byrne

Reference: Minatel E, et al. Abstract OC-0500. Presented at: European Society for Radiotherapy and Oncology Congress; April 26-30, 2019; Milan.

Disclosures: HemOnc Today could not confirm the authors’ relevant financial disclosures at the time of reporting.