NIMG-61. PATTERNS OF GLIOBLASTOMA RECURRENCE IN LOW FIELD INTENSITY REGIONS DURING TTFIELDS TREATMENT

Abstract

Glioblastoma (GBM) is an aggressive neoplasm that invariably recurs despite recent advances in therapy. Here, we describe a series of patients treated with Tumor Treating Fields (TTFields) who developed brain stem recurrence post TTFields therapy. TTFields is an FDA-approved therapeutic option for recurrent supratentorial GBM, as a monotherapy after surgical and radiation options have been exhausted, and recently in combination with maintenance temozolomide (TMZ) for treatment of newly diagnosed adult GBM patients. TTFields is a non-invasive, regional antimitotic treatment modality, alternating electric fields to tumors, through transducer arrays placed on the scalp of GBM patients. TTFields disrupts normal cell division processes, selectively targeting proliferating cancer cells. Some mechanisms of escape have been described (eg, out of field recurrence). It is known that the brainstem dose not receive high intensity TTFields due to anatomic limitations of the treatment delivery. Six cases were obtained by retrospective chart review from multiple providers that have experience with prescribing and planning treatment with TTFields. Clinical and radiographic reviews were performed after de-identification of patient records. Cases were compared according to demographics, tumor location and molecular genetics. Patients were a median age of 60 years old (range 52-69), who underwent standard therapy including surgery radiation, adjuvant TMZ, and subsequently received TTFields. There were various tumor locations at baseline presentation. Median duration of TTFields prior to development of brainstem recurrence was 3.5 months, range 2-5 months. Most patients discontinued treatment on TTFields after recurrence. Treatment options for patients with GBM are limited, however TTFields have been shown to improve OS when added to TMZ. TTFields can only be delivered in therapeutic intensities to the supratentorial brain. These out-of-field recurrences are of concern, given the stable primary supratentorial tumor. Further investigation is warranted to improve treatment of the entire nervous system with TTFields.