A retrospective pooled analysis of response patterns and risk factors in recurrent malignant glioma patients receiving a nitrosourea-based chemotherapy

Background: At recurrence the use of nitrosoureas is widely-used as a therapeutic option for glioblastoma (GBM) patients. The efficacy of fotemustine (FTM) has been demonstrated in phase II clinical trials; however, these papers report a wide range of progression-free-survival (PFS-6 m) rates, ranging from 21% to 52%. We investigated whether FTM could have a different response pattern in respect to time to adjuvant temozolomide failure, or whether specific independent risk factors could be responsible for the wide range of response rates observed. Methods: Recurrent GBM patients have been treated with fotemustine 75-100 mg/sqm at day 1, 8, 15 and after 4/5 weeks of rest with 100 mg/sqm every 21 days. Patients were stratified in 4 groups according to time to temozolomide failure: before starting (B0), during the first 6 months (B1), after more than 6 months of therapy (B2), and after a treatment-free interval (B3). Primary endpoint was PFS-6 m. A multivariable analysis was performed to identify whether gender, time after radiotherapy, second surgery and number of TMZ cycles could be independent predictors of the clinical benefit to FTM treatment. Results: 163 recurrent GBM patients were included in the analysis. PFS-6 m rates for the B0, B1, B2 and B3 groups were 25%, 28%, 31.1% and 43.8%, respectively. The probability of disease control was higher in patients with a longer time after radiotherapy (p = 0.0161) and in those who had undergone a second surgery (p = 0.0306). Conclusions: FTM is confirmed as a valuable therapeutic option for patients with recurrent GBM and was active in all study patient groups. Time after the completion of radiotherapy and second surgery are independent treatment-related risk factors that were predictive of clinical benefit.