Generalizability of clinical trial efficacy results to a real-world population: An example in migraine prevention.

Background: Health care decision makers are often concerned about the external validity of randomized controlled trials (RCTs), as their results may not apply to certain patients in the real world who intend to receive treatment.

Objective: To demonstrate a methodology for assessing the generalizability of clinical trial results to a real-world population, before sufficient and appropriate real-world effectiveness data are available, using individual patient-level data from an RCT and aggregated baseline data from a real-world French registry in migraine.

Methods: The analyses were conducted in 2 steps. First, individual patient-level baseline data from the multinational CONQUER RCT were weighted to match aggregated real-world InovPain registry patient characteristic data. Matched patient characteristics were sex, age, migraine type and duration, number of monthly migraine headache days, and number of monthly headache days at baseline. Second, the weighted CONQUER patient data were used to reanalyze the primary endpoint of CONQUER (least squares mean change from baseline in the number of monthly migraine headache days during the 3-month double-blind treatment phase) using predefined methodology. Sensitivity analyses were conducted to assess the robustness of findings.

Results: A total of 462 patients with migraine were randomized and treated with galcanezumab or placebo in CONQUER; aggregated InovPain data were available from 130 patients with migraine. We identified no important differences in baseline patient characteristics between the 2 prespecified populations, suggesting good external validity for CONQUER. Although this limited the extent of observed differences between the original and matched CONQUER populations, weighting of CONQUER data did help harmonize the 2 datasets and allow the results obtained in CONQUER to be generalized to patients more representative of the real-world French population with migraine. Results of weighted analyses suggested that galcanezumab would be superior to placebo for reducing monthly migraine headache days in a clinical trial in patients with episodic or chronic migraine who reflected the characteristics of patients eligible to receive the drug in France.

Conclusions: Findings suggest that our methods may be helpful for assessing the generalizability of clinical trial results to a real-world population before the availability of substantial real-world clinical data.