654 Fragility of functional/symptomatic endpoints to assess the efficacy of drugs for pulmonary arterial hypertension

Abstract

Abstract Aims Drugs for pulmonary arterial hypertension (PAH) have historically been evaluated for their efficacy in improving functional capacity and decreasing symptoms. However, these measures of treatment effect are approximate and subject to substantial variability, and therapeutic choices based on them may be aleatory. Methods and results We reviewed the articles reporting the results of phase 3 PAH randomized controlled trials (RCTs) and calculated the fragility index (FI) for the outcomes exploring functional capacity and symptoms. The FI corresponds to the number of events that need to be added to the arm with the smallest number of events to make a significant result non-significant: the lower the FI, the fragile the trial with respect to the endpoint examined. For RCTs with non-significant results, we calculated the FI as the number of events that need to be removed from the investigational drug (ID) group to reach a P-value <0.05. When possible, we also computed the FI for PAH hospitalization. Data about the rate of functional/symptomatic improvement were available for 22 (63%) of 35 RCTs (Table). The ID was superior to placebo or comparator with P < 0.05 in 10 (45%) of these 22 studies. The median FI was 2 [interquartile range (IQR): 6.5], with 4 RCTs having a FI = 1 and only 2 > 10 (Table). For the 12 RCTs in which the effect of the ID was neutral (P > 0.05), the median FI was 6 (IQR 4.25) (Table). The hospitalization FI was determined for 17 (77%) of the 22 RCTs and was overall higher than the one for the functional/symptomatic outcome (median 6, IQR 8). Conclusions Accessible information about the effects of PAH drugs on functional capacity and/or symptoms is published for 6 in 10 RCTs, in which very few events in one arm could have flipped the results from non-significant to significant or, more remarkably, from significant to non-significant. The evidence supporting the reduction of PAH hospitalizations as a treatment goal appears to be more robust.