# Randomised trial

Source: https://onco.cc/terms/randomised-trial/  
OnCo record `randomised-trial` (Term). Data CC BY-NC 4.0, attribute "Data from OnCo (onco.cc)"; commercial use needs a licence.

## TL;DR

A trial in which a coin toss (done by computer) decides which treatment each patient gets, so the groups are alike in every way except the treatment. It is the only reliable way to prove a treatment causes a benefit.

## Summary

Without randomisation, patients who receive a new drug tend to differ from those who do not (fitter, younger, treated at better centres), and those differences, not the drug, may explain a better outcome; randomising removes this bias, and analysing every patient in the group they were assigned to (intention-to-treat) preserves it. The control group receives the current standard of care, sometimes with a placebo added so that the two arms look identical, and the trial is powered so that a real difference of a given size is unlikely to be missed. Large randomised trials are slow and expensive, which is why surrogate endpoints, single-arm accelerated approvals and real-world evidence are all attempts to shortcut them, each with known pitfalls.

## Fields

- Kind: Term
- Last checked: 2026-09-09
- Also known as: randomised; randomized; randomisation; randomization; randomly assigned; randomised controlled trial; randomized controlled trial; RCT; RCTs; randomised trials; randomized trials; randomised phase 3; randomized phase 3; controlled trial; head-to-head; controlled trials; randomized trial

## Sources

- Wikipedia: https://en.wikipedia.org/wiki/Randomized_controlled_trial
- Wikipedia: https://en.wikipedia.org/wiki/Randomized_controlled_trial
- CONSORT statement: reporting randomised trials: https://www.consort-statement.org/

## Connected records

- terms: [Blinded trial](https://onco.cc/terms/blinding/), [Clinical equipoise](https://onco.cc/terms/clinical-equipoise/), [Clinical trial](https://onco.cc/terms/clinical-trial/), [Cluster-randomised trial](https://onco.cc/terms/cluster-randomised-trial/), [Confidence interval](https://onco.cc/terms/confidence-interval/), [Endpoint](https://onco.cc/terms/endpoint/), [Estimands and intercurrent events (ICH E9(R1))](https://onco.cc/terms/estimand/), [Hazard ratio (HR)](https://onco.cc/terms/hazard-ratio/), [Intention-to-treat (ITT) and per-protocol analysis](https://onco.cc/terms/intention-to-treat/), [Kaplan-Meier curve, censoring and proportional hazards](https://onco.cc/terms/kaplan-meier-curve/), [N-of-1 trial](https://onco.cc/terms/n-of-1-trial/), [Non-inferiority margin and equivalence trials](https://onco.cc/terms/non-inferiority-margin/), [Non-inferiority trial](https://onco.cc/terms/non-inferiority/), [P-value](https://onco.cc/terms/p-value/), [Phase 1, 2 and 3 trials](https://onco.cc/terms/trial-phases/), [Placebo](https://onco.cc/terms/placebo/), [Pragmatic trial](https://onco.cc/terms/pragmatic-trial/), [Real-world evidence](https://onco.cc/terms/real-world-evidence/), [Registry-based randomised trial](https://onco.cc/terms/registry-based-trial/), [SMART design (sequential multiple assignment randomised trial)](https://onco.cc/terms/smart-design/), [Standard of care](https://onco.cc/terms/standard-of-care/), [Stepped-wedge design](https://onco.cc/terms/stepped-wedge-design/), [Stratified randomisation, allocation concealment and minimisation](https://onco.cc/terms/stratified-randomisation/), [Why trials fail: underpowered, wrong endpoint, control arm drift, subgroup fishing, crossover](https://onco.cc/terms/trial-failure-modes/)
- trials: [ADAURA](https://onco.cc/trials/adaura/), [CHALLENGE (CCTG CO.21)](https://onco.cc/trials/challenge/), [CheckMate 067](https://onco.cc/trials/checkmate-067/), [INTERLACE](https://onco.cc/trials/interlace/), [ProtecT](https://onco.cc/trials/protect/)
- ideas: [Question prompt lists sent to patients before every major consultation](https://onco.cc/ideas/idea-moon-question-prompt-lists/)
- journals: [International journal of clinical oncology](https://onco.cc/journals/international-journal-of-clinical-oncology/), [The Lancet Haematology](https://onco.cc/journals/lancet-haematology/)

---
JSON: https://onco.cc/api/v1/entities/randomised-trial.json