Collin LC, Riis AH, MacLehose RF, et al. - Researchers utilize a newly extended validation study design for prospectively obtained validation data to validate predicted colorectal cancer (CRC) recurrences against gold standard diagnoses from medical records in an actively followed cohort of CRC patients in Denmark. The Bayesian monitoring framework was used in clinical trials to iteratively modernize classification parameters (positive and negative predictive values, and sensitivity and specificity) in an adaptive validation substudy design. In Denmark, there were 63 recurrences diagnosed by active follow-up and 70 recurrences distinguished by a predictive algorithm, among 355 men and women diagnosed with CRC and actively followed semi-annually. The data indicated the ability of the method to accurately define when sufficient validation data have been collected, in this proof of concept application of the adaptive validation study design for outcome misclassification. This approach helps as a novel validation substudy design for prospectively collected data with the simultaneous implementation of a validation study.