Purpose: Predictive marker of bevacizumab activity is an unmet medical need. Our objective was to evaluate the trough concentration of bevacizumab in patients with recurrent glioblastoma and to analyze its potential association with patient characteristics and outcome.
Methods: We retrospectively included patients with recurrent glioblastoma treated with bevacizumab and chemotherapy with available plasma collected before the second bevacizumab administration (residual time). Trough bevacizumab concentrations and antibodies against bevacizumab were quantified by enzyme linked immunosorbent assay (ELISA).
Results: We included 21 patients with a median age of 63.4 years at bevacizumab initiation. Occurrence of antibody against bevacizumab was not observed. Median pre-cycle 2 trough concentration of bevacizumab was 87.1 µg/mL (range, 21.7 µg/mL -151.8 µg/mL). Trough concentration of bevacizumab was not correlated to patient age (p=.529), gender (p=.622), weight (p=.403), size (p=.871), Body Mass Index (p=.439), Karnofsky Performans Status (p=.988) and steroid intake (p=0.403). No correlation was found between trough bevacizumab concentration and response rate (p=.856). The highest tertile of trough bevacizumab concentration tended to be associated with poor progression-free survival (p=0.152), while no correlation was observed for overall survival.
Conclusion: Evaluation of the trough concentration of bevacizumab during treatment for patients with glioblastoma is feasible and highly variable. Its prognostic value should be explored in prospective trial.