# Intention-to-treat (ITT) and per-protocol analysis

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

## TL;DR

Analysing every patient in the group they were randomised to, whether or not they actually took the treatment. It preserves the fairness of randomisation and reflects what happens when a treatment is prescribed in real life; per-protocol analysis, by contrast, counts only those who complied.

## Summary

ITT is the primary analysis for superiority trials because excluding non-compliers or early dropouts reintroduces bias. Per-protocol analyses matter for non-inferiority trials, where non-compliance can mask a real difference. 'Modified ITT' variants exclude patients who never received a dose or lacked a baseline measurement and should be pre-specified. 'Response-evaluable' populations in single-arm trials inflate response rates by dropping early progressors, and 'safety population' counts patients as treated. Trial and drug pages on this site report ITT results unless stated.

## Fields

- Kind: Term
- Last checked: 2026-09-09
- Also known as: ITT; intention-to-treat; intent-to-treat; ITT population; ITT analysis; modified intention-to-treat; mITT; per-protocol; per protocol; per-protocol population; as-treated; evaluable population; efficacy-evaluable; response-evaluable; safety population; full analysis set; analysis population; randomised population

## Sources

- Wikipedia: https://en.wikipedia.org/wiki/Intention-to-treat_analysis
- Wikipedia: https://en.wikipedia.org/wiki/Intention-to-treat_analysis

## Connected records

- terms: [Blinding (double-blind, open-label, placebo-controlled)](https://onco.cc/terms/double-blind/), [Control arm and comparator (investigator's choice)](https://onco.cc/terms/control-arm/), [Estimands and intercurrent events (ICH E9(R1))](https://onco.cc/terms/estimand/), [Non-inferiority margin and equivalence trials](https://onco.cc/terms/non-inferiority-margin/), [Non-inferiority trial](https://onco.cc/terms/non-inferiority/), [Pre-specified vs post-hoc analysis](https://onco.cc/terms/prespecified-vs-post-hoc/), [Randomised trial](https://onco.cc/terms/randomised-trial/), [Why trials fail: underpowered, wrong endpoint, control arm drift, subgroup fishing, crossover](https://onco.cc/terms/trial-failure-modes/)
- fronts: [Drug Discovery Platforms](https://onco.cc/fronts/drug-discovery/)
- trials: [PERSEPHONE](https://onco.cc/trials/persephone/), [TAILORx](https://onco.cc/trials/tailorx/)

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JSON: https://onco.cc/api/v1/entities/intention-to-treat.json