Abstract

Purpose: To analyze long term outcomes of IDH negative Glioblastoma in elderly treated by two different fractionation regimens. To assess the impact of proportion of necrosis in the index lesion on the long term outcomes

Materials and Methods: A cohort of 14 elderly patients (mean age= 65 years) with Glioblastoma had undergone radiotherapy (Group A, 7: conventional fractionation; Group B, 7: hypofractionation). Patients in Group A had undergone conventional radiotherapy schedule (60Gy in 30 fractions over 6 weeks with concurrent TMZ), while patients in group B had undergone Hypofractionated radiotherapy (35Gy in 10 fractions in the first phase and further RT was based on response). Concurrent chemotherapy with Temozolomide in group B was administered if MGMT promoter methylation was found on methylation specific PCR. We retrospectively reviewed the index post Gado T1W images of all the patients to assess the proportion of necrosis calculated mathematically and termed Tumour Necrotic index (TNI) (defined by ratio of Volume (cc) of Gadolinium enhanced necrotic cavity and solid components of the mass lesion). The data was tabulated on SPSS version 21.0 and various outcomes measures analysed.

Results: Mean age of the group was 65 years, median KPS was 70. Among patients in Group A, 80% had undergone maximal safe resection, while 80% in group B they had undergone only a biopsy (3open:1STB) for histological confirmation. IDH testing by IHC against IDH1-R 132H was negative for all the patients in both groups while one patient in group B had methylated promoter of MGMT. In Group A, there was increased incidence of opportunistic infections, biochemical & metabolic alterations, prolonged overall treatment time of radiotherapy compared to Group B. Only 30% of the patients in Group A completed planned therapy. At a median follow up of 12 months, none of the patients in Group A are alive, whereas OS in Group B is 20% (Logrank, p= 0.01). Univariate analysis showed that TNI ratio of <0.3 (p= 0.03) and Hypofractionated schedule of radiotherapy (0.01) showed significant impact on overall survival.

Conclusion: We recommend Hypofractionated radiotherapy as the regimen of choice in Elderly patients with IDH negative Glioblastoma. A simple radiological tool- TNI aids in identifying elderly patients with Glioblastoma who will benefit by Hypofractionated radiotherapy.