Early Gamma Knife Therapy (Without EBRT) in Operated Patients of Glioblastoma Multiforme

Background: The standard therapy for glioblastoma (GBM) has been external beam radiotherapy (EBRT) with concomitant temozolomide (TMZ) given for six cycles, after maximum possible surgical resection although recurrences after chemoradiation are mostly in-field. Objective: To compare the effects of early GKT (without EBRT) along with TMZ to those receiving standard chemoradiotherapy (EBRT + TMZ) after surgery. Methods: This was a retro-prospective study on histologically proven GBMs operated at our center between January 2016 and November 2018. The EBRT group consisted of 24 patients who received EBRT + TMZ for six cycles. The GKT arm consisted of 13 consecutive patients who received Gamma Knife within 4 weeks of surgery along with lifelong temozolomide. Patients were followed up every 3 months with CEMRI brain and PET-CT. The primary endpoint was overall survival (OS) with progression-free survival (PFS) being the secondary endpoint. Results: At a mean follow-up of 13.7 months, the median overall survivals in GKT and EBRT groups were 11.07 and 13.03 months, respectively (HR = 0.59; P value = 0.19; 95% CI: 0.27-1.29). The median PFS for GKT group was 7.03 months (95% CI: 4.17-17.3) as compared to 11.07 months (95% CI: 5.33-14.03) for the EBRT group. There was no statistical difference in the PFS or OS between the GKT and EBRT groups. Conclusion: Our study shows that Gamma Knife therapy (without EBRT) to residual tumor/tumor bed after primary surgery with concurrent temozolomide has similar progression-free (PFS) and overall survival (OS) rates when compared to conventional treatment (EBRT).