P09.12 Durable remission with tumor treating fields as adjuvant treatment for glioblastoma relapse in a patient with Grad IV hematotoxicity during initial temozolomide radiochemotherapy

Abstract

We report on a 53 years old female patient who was diagnosed with a left temporal tumor with significant perifocal edema in August 2015. A microsurgical, neuronavigation-guided gross total resection was performed and glioblastoma was diagnosed histologically. On immunohistochemistry, staining for IDH1-mutations was negative. Methylation analysis revealed a methylated MGMT promotor. One month after resection, the patient started a radiochemotherapy with temozolomide (TMZ) 75mg/m2 per day and radiation fractions of 1.8 Gy with a planned dose of 50.4 Gy and a boost of the tumor region up to a total dose of 60.4 Gy. After 4 weeks the radiochemotherapy was interrupted because of pancytopenia with grade 4 thrombocytopenia (minimal platelets 4000/µl) and grade 3 leukopenia (minimal WBC 1170/µl). The patient was transfused with 8 units of platelets and 6 units of packed erythrocytes. After an interruption of one month WBC were above 2000/µl and platelets above 20000/ml, hence radiation therapy was resumed without concomitant TMZ. On a follow-up MRI in February 2016 a tumor relapse was detected. A second resection of the left temporal tumor was performed and because of a persisting thrombocytopenia with platelets below 100 000/µl, we offered the patient an adjuvant treatment with tumor treating fields (TTF) alone. TTF started in May 2016 and was well tolerated. Except from minor skin reactions, which were managed with ointments, the patient denied any adverse reactions. The latest MRI from September 2016 showed an ongoing remission, and at the most recent clinical follow-up in November 2016 there was no sign of neurological impairment. Hence, the second remission lasts now as long as the first remission, but with a much better toxicity profile of TTF compared to the initial radiochemotherapy. TTF therapy alone might therefore represent an alternative treatment option for patients with relapsed glioblastoma for whom chemotherapy is contraindicated.