Posted by Michael Wonder on 05 Apr 2017
Differences in treatment effect size between overall survival and progression-free survival in immunotherapy trials: a meta-epidemiologic study of trials with results posted at ClinicalTrials.gov
4 April 2017 - Tan et al. compared treatment effect sizes between overall survival and progression-free survival in trials of US FDA–approved oncology immunotherapy drugs with results posted at ClinicalTrials.gov.
They identified 51 trials assessing 14 drugs across 15 conditions. Treatment effect sizes were 17% greater, on average, with progression-free survival (PFS) than with overall survival (OS) (rHR, 0.83; 95% CI, 0.79 to 0.88; I2 = 34.4%; P = .01; τ2 = 0.0129). Nearly one half of the trials (n = 23, 45%) showed statistically significant benefits for PFS but not for OS. Differences were great for trials for three Genentech/Roche medicines: obinutuzumab (rHR, 0.21; 95% CI, 0.08 to 0.54), bevacizumab (rHR, 0.75; 95% CI, 0.67 to 0.84), and rituximab (rHR, 0.79; 95% CI, 0.64 to 0.98). The coefficient of determination was 38% and the surrogacy threshold effect was 0.50.
Treatment effect sizes in trials of immunotherapy drugs were greater for PFS than for OS, with important differences for some drugs, which is consistent with surrogacy metrics. Caution must be taken when interpreting PFS in the absence of OS data.
