{"entity":{"id":"idea-tr1-bayesian-borrowing-smaller-controls","kind":"idea","name":"Borrow from past control arms to shrink the control group in phase 3","aka":[],"tldr":"When the standard treatment has been given to thousands of similar patients in earlier trials, a new trial could randomise fewer people to it and lean on that history, as long as the old data still matches.","summary":"Hybrid control designs use Bayesian dynamic borrowing (power priors, meta-analytic-predictive priors, commensurate priors) from curated historical control arms and real-world cohorts to reduce concurrent control allocation to 1:2 or 1:3 while retaining randomisation. Borrowing is down-weighted automatically when the concurrent controls diverge from history. The FDA Complex Innovative Design programme has reviewed such designs; oncology uptake is limited.","asOf":"2026-09-08","links":[{"label":"FDA Complex Innovative Trial Design meeting programme","url":"https://www.fda.gov/drugs/development-resources/complex-innovative-trial-design-meeting-program"}],"tags":[],"related":[],"cancers":["nsclc","colorectal"],"sections":[],"technologies":[],"targets":[],"drugs":[],"companies":[],"institutions":[],"pathways":[],"terms":["hazard-ratio","standard-of-care"],"trials":[],"people":[],"bottlenecks":["b-trial-design","b-trial-enrolment"],"keyPapers":[],"journals":[],"dependsOn":[],"notes":[],"hypothesis":"Hybrid-control phase 3 trials in well-characterised indications will reach the same decision as a conventional 1:1 trial with 25-40 percent fewer control patients and shorter accrual, and the borrowing weight will correctly fall when historical drift exists.","rationale":"Control-arm outcomes in first-line NSCLC, metastatic breast and CRC are stable across recent trials with the same regimen; requiring 400 fresh control patients every time is a cost paid by patients as well as sponsors.","test":"Re-analyse three completed phase 3 trials as if run with dynamic borrowing from pre-existing control data; confirm identical conclusions. Then run one prospective hybrid trial under the CID programme.","maturity":"early-clinical","actor":"industry","cost":"medium","horizonYears":3},"route":"/ideas/idea-tr1-bayesian-borrowing-smaller-controls/","neighbours":{"cancer":[{"id":"colorectal","kind":"cancer","name":"Colorectal cancer","route":"/cancers/colorectal/"},{"id":"nsclc","kind":"cancer","name":"Non-small-cell lung cancer","route":"/cancers/nsclc/"}],"term":[{"id":"hazard-ratio","kind":"term","name":"Hazard ratio (HR)","route":"/terms/hazard-ratio/"},{"id":"standard-of-care","kind":"term","name":"Standard of care","route":"/terms/standard-of-care/"}],"bottleneck":[{"id":"b-trial-design","kind":"bottleneck","name":"Trial design, endpoints and cost","route":"/bottlenecks/b-trial-design/"},{"id":"b-trial-enrolment","kind":"bottleneck","name":"Trials enrol too few, too slowly","route":"/bottlenecks/b-trial-enrolment/"}]}}