Resolution of cystic enhancement to add-on tumor treating electric fields for recurrent glioblastoma after incomplete response to bevacizumab.

The NovoTTF-100A device emits alternating tumor treating electric fields (TTFields) that interfere with cytokinesis and chromosome segregation during mitosis. Because it has a similar efficacy to cytotoxic chemotherapy, the device has been approved by the United States Food and Drug Administration for the treatment of recurrent glioblastoma. Although bevacizumab has been in use for recurrent glioblastoma, patients who experience incomplete or no response to bevacizumab may be predisposed to early bevacizumab treatment failure. However, the addition of TTFields therapy may augment the efficacy from bevacizumab. We report a patient with recurrent cystic glioblastoma who received add-on TTFields therapy due to an incomplete response to single-agent bevacizumab. After 6 cycles of therapy, a resolution of cystic enhancement was noted, together with reduction of the tumor cyst and resolution of most of the cerebral edema in the surrounding brain. However, the patient also suffered from relapsed disease at locations distant from the original glioblastoma and the corresponding radiation fields received at initial diagnosis. We conclude that combination TTFields and bevacizumab therapy is safe and may be efficacious for patients with recurrent glioblastoma. A further study would be needed to determine the relapse pattern and the distribution of the electric fields in the brain.