Radiation induced early necrosis in patients with malignant gliomas receiving temozolomide

Temozolomide is the major drug in the treatment of malignant gliomas. Radiation induced necrosis can behave radiologically and clinically like a recurrent tumor. The major problem is the differentiation between recurrence and radiation injury especially in early phases of treatment. The aim of this study was to evaluate the patients receiving temozolomide showing early clinical or radiological progression and impact of early necrosis on follow-up.

We retrospectively evaluated medical records of 67 patients with malignant glioma receiving temozolomide. All patients received concomitant radiotherapy and temozolomide followed by adjuvant temozolomide. In case of any radiological or clinical progression, MRI spectroscopy evaluation was used to confirm tumoral progression.

Radiological or clinical progression was observed in 17 (25.4%) patients. Early radiation induced necrosis was diagnosed in 4 of 17 patients (23.5%) by surgery (n=3) and MRI spectroscopy (n=1). The observed incidence of pseudoprogression was 4 in 67 (6%) patients. Patients with diagnosis of early radiation injury had median progression-free survival of 7 months compared to 5 months in patients without radiation damage (p=0.004). However, there was no statistically significant difference in terms of overall survival between groups.

Temozolomide can cause early radiation induced injury which can mimic progressive tumor. Although the discrimination between two entities results in the accurate evaluation of response to therapy and benefits those patients, it did not affect overall survival. MRI spectroscopy is a valuable tool to define early radiation necrosis and should be further evaluated in larger prospective studies.