The Addition of Chloroquine to Chemoradiation for Glioblastoma

Patients with a glioblastoma (GBM) have a poor prognosis with a median survival of 14.6 months after maximal treatment with a resection and chemoradiation. Since the pivotal trial evaluating the effect of temozolomide (TMZ), overall survival has not increased. Treatment of GBM xenografts in vivo with chloroquine (CQ), an antimalarial agent, has been shown to reduce the hypoxic fraction and sensitizes tumors to radiation. Epidermal growth factor receptor (EGFR) amplification or mutation is regularly observed GBM and is thought to be a major contributor to radioresistance. The most common EGFR mutation in GBM (EGFRvIII) is present in 50-60% of patients whose tumor shows amplification of EGFR. EGFR provides cells with a survival advantage through autophagy when exposed to stresses such as hypoxia and nutrient starvation. This effect is even more pronounced in EGFRvIII overexpressing tumors. Previously, the potential effect CQ has been demonstrated in a small randomized controlled trial in GBM treated with radiotherapy and carmustine, which showed a trend towards increased overall survival. However, as the intracellular effects of chloroquine are dose-dependent the maximum tolerated dose for CQ in combination with concurrent radiotherapy with daily temozolomide needs to be established.