Evaluation of chemoresponse assays as predictive markers

Background: A chemoresponse assay that can be used to predict which patients will respond to which drugs would be useful in directing treatment. Two new analytic methods to assess the predictive ability of a chemoresponse assay have been proposed by Tian et al. Methods: Three examples in which a hypothetical assay has no predictive ability are considered to evaluate the properties of the proposed analytic methods. Results: For these specific examples, the proposed methods incorrectly suggest that the assay is predictive. Conclusions: The examples presented here demonstrate that it can be challenging to evaluate the predictive value of a chemoresponse assay.