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Updated: Jul 28, 2025

Evaluating the Effectiveness of Cancer Drug Sensitization In Vitro and In Vivo
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Published on: February 6, 2015

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A Systematic Review and Pooled Analysis of Hypothesized versus Observed Effect Sizes in Early Phase Cancer Prevention

Jens Eickhoff1, Jen Zaborek1, Guanhua Chen1

  • 1Department of Biostatistics and Medical Informatics, University of Wisconsin School of Medicine and Public Health, Madison, Wisconsin.

Cancer Prevention Research (Philadelphia, Pa.)
|May 31, 2023
PubMed

Insights

Early phase cancer prevention trials often fail to detect intervention effects. Pooled analyses reveal observed effect sizes are significantly smaller than hypothesized, necessitating careful trial design and sample size planning.

Area of Science:

  • Oncology
  • Clinical Trials
  • Preventive Medicine

Background:

  • Early phase cancer prevention trials aim to assess safety, tolerability, feasibility, and efficacy signals of preventive agents.
  • Many early phase chemoprevention trials do not detect hypothesized intervention effects, leading to potential failures in identifying promising agents.
  • Understanding the discrepancy between hypothesized and observed effect sizes is crucial for optimizing trial design and resource allocation.

Approach:

  • A systematic review and pooled analysis were conducted on early phase (Phase 0/I/II) chemoprevention trials.
  • Fifty-nine trials were evaluated, with 24 selected for analysis based on complete data for hypothesized and observed effect sizes.
  • Pooled analysis examined the ratio of observed to hypothesized effect sizes using a random-effects model.

Key Points:

  • The pooled estimate showed observed effect sizes were 0.57 times the hypothesized effect sizes (95% CI: 0.42-0.73, P < 0.001).
  • This significant reduction in observed effect sizes was consistent across various subgroup analyses.
  • The findings highlight a consistent overestimation of efficacy in the initial planning of these trials.

Conclusions:

  • Early phase cancer chemoprevention trials frequently yield smaller observed effect sizes than initially hypothesized.
  • Accurate sample size calculations must balance detectable effect sizes with realistic population accrual for cost-effectiveness.
  • Careful planning of study design, primary endpoints, and sample size is essential for successful early phase chemoprevention trials.

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