Performance of Control Arms in Trials Leading to FDA Cancer Drug Approvals

Area of Science:

• Oncology
• Clinical Trial Design
• Drug Development

Background:

• Selecting appropriate control arms is critical for evaluating the efficacy of novel anticancer therapies.
• Control arm performance significantly impacts the interpretation of new drug trial results.
• Inconsistent control arm outcomes can affect the perceived benefit of experimental treatments.

Purpose of the Study:

• To analyze the performance of control arms in clinical trials supporting FDA drug approvals for advanced solid cancers.
• To identify the frequency and extent of control arm underperformance and overperformance.
• To assess the implications of control arm discrepancies on drug approval and efficacy assessment.

Main Methods:

• Analysis of progression-free survival (PFS) in control arms of Phase III or double-arm Phase II trials for FDA-approved anticancer drugs (2014-2023).
• Extraction of assumed median PFS (amPFS) from protocols and observed median PFS (omPFS) with confidence intervals from trial results.
• Categorization of control arms as underperforming (amPFS > omPFS upper bound), outperforming (amPFS < omPFS lower bound), or within range.

Main Results:

• Out of 72 trials, 33.3% of control arms underperformed, 11.1% outperformed, and 55.5% were within range.
• Underperformance was notable in trials for immune checkpoint inhibitors (48.0%) and targeted therapies (18.9%).
• Significant discrepancies (>20%) between assumed and observed PFS occurred in 75.0% of underperforming arms, with 38.9% of expedited approvals lacking demonstrated overall survival advantage.

Conclusions:

• Shorter-than-expected progression-free survival in control arms may inflate the perceived efficacy of new anticancer drugs.
• Accurate analysis and realistic assumptions for control arm outcomes are essential for robust efficacy assessment.
• Improved control arm evaluation is crucial for reliable drug development and patient treatment decisions.