# Delayed Pseudoprogression in Glioblastoma Patients Treated With Tumor-Treating Fields

## TL;DR

Two glioblastoma patients treated with TTFields showed delayed pseudoprogression, appearing six months after radiation therapy, which is later than typical cases.

## Contribution

This report highlights a novel case of delayed pseudoprogression specifically associated with TTFields treatment in glioblastoma patients.

## Key findings

- Two glioblastoma patients showed radiographic signs of pseudoprogression six months after radiation therapy.
- In one case, pathology confirmed treatment effect rather than true progression.
- Steroid therapy resolved the pseudoprogression in another patient.

## Abstract

Tumor-treating fields (TTFields) is an established treatment modality for glioblastoma. False progression to chemoradiation is a known problem in patients with glioblastoma multiforme (GBM), with most cases occurring within three months of radiation therapy. In this report, we present two cases of delayed pseudoprogression caused by TTFields. Two patients with GBM who received TTFields showed signs of radiographic progression six months after the completion of radiation therapy. Patient 1 was a 37-year-old female with a glioblastoma in the right temporal lobe. Patient 2 was a 70-year-old male with glioblastoma in the left temporal lobe. Both patients received radiation therapy, followed by temozolomide (TMZ) maintenance therapy and TTFields. Patient 1 underwent a second resection; however, the pathology revealed only a treatment effect, and the final diagnosis was a pseudoprogression. In Case 2, the disease resolved with steroid therapy alone. In both patients, the lesions appeared later than during the typical pseudoprogression period. A recent study reported that TTFields increase the permeability of the plasma cell membrane, which may result in further leakage of gadolinium into the extracellular lumen. Further studies are needed to better characterize delayed pseudoprogression and improve treatment outcomes.