Originally published as JCO Early Release 10.1200/JCO.2008.19.6709 on July 27 2009

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Comparison of Power Between Randomized Discontinuation Design and Upfront Randomization Design on Progression-Free Survival

From the Departments of Epidemiology and Biostatistics and Hematology/Oncology, Case Comprehensive Cancer Center, Case Western Reserve University, Cleveland, OH.

Corresponding author: Pingfu Fu, PhD, Department of Epidemiology and Biostatistics, Case Western Reserve University, 10900 Euclid Ave, Cleveland, OH 44106; e-mail: pxf{at}bfox.cwru.edu.

Purpose Enrichment based on molecular characteristics has emerged as an important inclusion criterion in phase II trials of targeted anticancer agents. In this study, we evaluate a well-described method of population enrichment by tumor growth characteristics in the early development stage of targeted cytostatic agents.

Methods For some solid tumors, such as pancreatic carcinoma, using a time-to-event end point (eg, time to disease progression) to evaluate the efficacy of a cytostatic agent in a phase II trial is more relevant than clinical response by Response Evaluation Criteria in Solid Tumors. In this setting, we compared the power of the randomized discontinuation and upfront randomization designs under two previously proposed tumor growth models for treatment effect when the end point is time-to-event.

Results By selecting patients with more homogeneous tumor growth characteristics, the randomized discontinuation design is more efficient than the upfront randomization design when treatment benefit is restricted to slow-growing tumors. Under a model where only a subset of patients expressing the molecular target are sensitive to the agent, the randomized discontinuation design is more powerful than the upfront randomization design when the treatment effect is small; and vice versa when the treatment effect is moderate to large.

Conclusion For selected targeted agents where a bioassay to select patients expressing the specific molecular target is not available, the randomized discontinuation design is a feasible alternative patient enrichment strategy in certain disease settings and provides a reasonable platform to evaluate drugs before phase III testing.

Supported by Grant No. U01 CA62502 from the National Institutes of Health.

Authors' disclosures of potential conflicts of interest and author contributions are found at the end of this article.

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