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PFS may be surrogate for OS in glioblastoma
A large meta-analysis showed a strong correlation between PFS and OS in patients with glioblastoma, suggesting PFS could be an appropriate surrogate endpoint.
Researchers reviewed data from 91 phase 2 and 3 glioblastoma trials to assess the power of PFS and objective response rate as potential surrogate endpoints for OS.
Results revealed a strong correlation between PFS and OS (regression coefficient [R2]=0.92; 95% CI, 0.71-0.99). Also, results of linear regression analysis showed a 10% PFS risk reduction yielded an 8.1% OS risk reduction.
R2 between median PFS and OS was 0.70 (95% CI, 0.59–0.79). Researchers observed higher R2 values in trials that utilized Response Assessment in Neuro-Oncology (R2=0.96; n=8) vs. Macdonald criteria (R2= 0.70; n=83). However, the investigators observed no significant differences between treatment regimens that contained temozolomide (Temodar, Schering-Plough) or bevacizumab (Avastin, Genentech; P=.10).
Results showed a significantly higher regression line slope between median PFS and OS among patients with newly diagnosed disease compared with those with recurrent disease (0.58 vs. 0.35; P=.04). R2 for 6-month PFS with 1-year OS and median OS were 0.60 (95% CI, 0.37-0.77) and 0.64 (95% CI, 0.42-0.77), respectively.
Researchers noted a poor correlation between objective response rate and OS (R2=0.22).
Disclosure: The researchers report financial relationships with Apogenix, Boehringer Ingelheim, Eli Lilly, F. Hoffmann-La Roche, Genentech, Merck and MSD.