The gender effect in stroke thrombolysis - Of CASES, controls, and treatment-effect modification

Background: Large studies of patients with acute stroke not receiving thrombolytic therapy have repeatedly demonstrated poorer outcomes for women compared to men. An analysis of five pooled randomized controlled trials testing IV recombinant tissue plasminogen activator (rtPA) demonstrated that rtPA benefits women more than men; the usual gender difference, apparent among controls, was totally nullified in the rtPA group. This nullification of the usual gender effect among rtPA-treated patients has not been confirmed. Methods: We analyzed baseline characteristics and functional outcomes in men vs women in the Canadian Alteplase for Stroke Effectiveness Study (CASES), a multicenter study that collected outcomes data for patients treated with rtPA in Canada to assess the safety and effectiveness of alteplase for stroke in the context of routine care. Results: Among 1,110 patients, including 615 men and 505 women, a normal or near normal outcome at 90 days was found in 37.1% of men vs 36.0% of women (p = 0.71). This was essentially unchanged after adjusting for differences in baseline characteristics, including age > 70, glucose, hypertension, atrial fibrillation, hypercholesterolemia, baseline National Institute of Health Stroke Severity, and baseline Alberta Stroke Program Early CT score (35.2% in men vs 38.2% in women, p = 0.332). Ninety-day mortality was similar between the sexes in both the adjusted and unadjusted analysis. Conclusions: There was no difference in 90-day outcomes in recombinant tissue plasminogen activator (rtPA)-treated men and rtPA-treated women. This is consistent with the pooled analysis of randomized controlled trials, showing greater benefit for thrombolysis in women and nullification of the usual gender difference in outcome.