Authors: Silberstein SD et al., J Neurol Neurosurg Psychiatry 2014 Dec 12;
Most chronic migraineurs who ultimately respond to onabotulinumtoxinA do so with the first cycle, but a proportion of initial nonresponders may respond to a second or third cycle.
In this manufacturer-funded study, researchers examined how many chronic migraineurs who do not respond to the first cycle of onabotulinumtoxinA will respond to the second or third cycle. The researchers used pooled data from two multicenter PREEMPT trials conducted in North America and Europe, both with a 4-week baseline period followed by two 12-week treatment cycles that were double-blinded, randomized, and placebo-controlled (onabotulinumtoxinA vs. saline injections). Subsequently, three 12-week treatment cycles were unblinded. This responder analysis was performed on the onabotulinumtoxinA arm (n=688).
After the first cycle of treatment, 49.3% of patients experienced a ≥50% reduction in headache days during at least one month. An additional 11.3% of the 688 patients first achieved this outcome after the second cycle and 10.3% after the third (unblinded) cycle. Comparable proportions were seen for secondary outcomes (moderate-to-severe headache days and total cumulative hours of headache), using both ≥50% reduction and a more lenient ≥30% reduction to indicate response. The 50% and 30% responder rates after the first two cycles of treatment in the placebo arm were not provided.
This analysis suggests that a small proportion of patients who do not respond to the first treatment with onabotulinumtoxinA may respond to a second or third cycle. However, the data are difficult to interpret without the ≥50% responder rates in the placebo arm after the first two cycles, as the placebo response was high in the PREEMPT trials (mean reduction, 6–7 headache days per month). Furthermore, unblinding occurred after the second cycle, with an unknown effect on the response rate to the third onabotulinumtoxinA treatment. The data provided in this analysis are insufficient to recommend a second or third cycle of onabotulinumtoxinA.