Radt-61. A Pilot Study to Evaluate Safety and Feasibility of Adjuvant Hypofractionated Stereotactic Radiotherapy With Concurrent and Adjuvant Temozolomide in Patients With Newly Diagnosed GBM

BACKGROUND The standard of care treatment for glioblastoma multiforme (GBM) is maximal safe resection followed by postoperative radiation with concurrent and adjuvant temozolomide. The adjuvant radiotherapy dose is 60Gy in 30 fractions, 2Gy per fraction over 6 weeks with concurrent temozolomide 75mg/m2. The median overall survival is 14.6 months. Hypofractionated stereotactic radiotherapy enables to deliver high biological effective dose with shorter treatment duration.Aims: In this prospective study, we aimed to evaluate the safety and feasibility of adjuvant hypofractionated stereotactic radiotherapy technique(HFSRT)with conventional fractionated radiotherapy (CRT) with concurrent and adjuvant temozolomide. METHODS Fifteen adult patients diagnosed with GBM and ECOG performance status of 0-1 were include in the study from August 2019 to April 2021. All patients underwent maximal safe resection. Seven patients received adjuvant HFSRT to a dose of 42Gy in six fractions, 7Gy per fraction on alternate days over 2 weeks with concurrent and adjuvant temozolomide. Eight patients received conventional radiotherapy to a dose of 60Gy in 30 fractions over six weeks with concurrent and adjuvant temozolomide. All patients received adjuvant radiotherapy with VMAT technique. Concurrent temozolomide was given at a dose of 75mg/m2 daily during treatment. Adjuvant temozolomide at a dose of 150mg/m2 for first cycle and 200mg/m2 afterwards for a total of 6 cycles. RESULTS The mean age of all patients included in the study was 39.9 years. Eight patients were males and seven were females. Seven out of 15 patients underwent gross total resection. All patients completed adjuvant radiotherapy treatment without any interruptions. The commonly observed side effects of CTCAE grade1cognitive impairment, grade1seizures, Grade 1 and 2 muscle weakness, grade 1 somnolence and grade 1 thrombocytopenia were not significantly different among two treatment groups. However, Grade 3 hyponatremia was observed in two patients who received conventional treatment during adjuvant temozolomide. CONCLUSION Adjuvant hypofractionated stereotactic radiotherapy with concurrent and adjuvant temozolomide appears to be safe and feasible treatment option, which requires further studies in patients with GBM.