Adding intraoperative radiotherapy to the standard of care for patients with newly diagnosed glioblastoma appear to offer improved local control and survival, compared with those of historical controls without major adverse events, according to authors of a pooled analysis.
Among 51 patients who underwent tumor resection followed by intraoperative radiotherapy (IORT), standard adjuvant chemoradiotherapy, and chemotherapy maintenance, the estimated 2-year overall survival (OS) rate was 38.7%, compared with 26.5% at 2 years for patients who had received external beam radiotherapy (EBRT) and concomitant plus adjuvant temozolomide in a multinational, reported Gustavo Sarria, MD, from University Medical Center Mannheim (Germany) and colleagues.
The median local progression-free survival (L-PFS) at a median follow-up of 18 months was 16 months, and the median distant PFS (D-PFS) was 30 months, indicating effective delay of tumor recurrence in a substantial proportion of patients.
“Intraoperative radiotherapy does not require extra radiation to travel through healthy tissue as compared to EBRT, thus allowing for local dose escalation at the site of most likely recurrence,” they wrote in.
The investigators performed a retrospective analysis of data on a total of 51 patients with a median age of 55 years who were treated with IORT and standard of care at five centers in Germany, Perum, and China. The patients all underwent brain surgery followed by a single IORT application at doses ranging from 10 to 40 Gy, with low-energy (50-kV) x-rays.
Following surgery, all patients received 60-Gy intensity-modulated or volumetric-modulated arc (IMRT-VMAT) EBRT and concomitant temozolomide chemotherapy followed by maintenance temozolomide.
At a median follow-up of 18 months the median OS was 18 months, median overall PFS was 11.4 months, median L-PFS (new lesions 1 cm or less from the tumor cavity border) was 16 months, and median D-PFS (new lesions more than 1 cm from the tumor cavity border) was 30 months.
The estimated Kaplan-Meier 1-, 2-, and 3-year OS rates were 79.5%, 38.7%, and 25.6%, respectively. The estimated median PFS over the same time points was 46.2%, 29.4%, and 5.9. The 1-, 2-, and 3-year estimated L-PFS was 60.9%, 37.9%, and 12.6%, and D-FPS rates were 76.7%, 65.0%, and 39.0% respectively.
In slightly more than one-third of the cases (35.3%), the first progression occurred locally. Grade 1 radionecrosis occurred in 7.8% of patients, and 17.6% had grade 3 radionecrosis. There were no grade 4 toxicities reported, and no treatment-related deaths.
The investigators noted that IORT added to standard of care is being tested against standard care alone in a multinational phase 3 randomized trial ().
The authors did not receive outside funding for the study. Dr. Sarria reported Grants from Carl Zeiss Meditec outside the submitted work.
SOURCE: Sarria G et al. J Rad Oncol. 2019 Oct 16. .