# Blinding (double-blind, open-label, placebo-controlled)

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

## TL;DR

Whether patients and doctors know which treatment is being given. Double-blind: neither knows (a placebo hides it). Open-label: both do, unavoidable for surgery or radiotherapy but a source of bias when judging progression and symptoms.

## Summary

Blinding protects subjective outcomes (progression on scans, symptom scores, decisions to stop or switch) from expectation bias. Many oncology trials are open-label because the comparators differ in route or schedule; they compensate with blinded independent central review of imaging and hard endpoints such as overall survival. Placebo-controlled designs are standard for maintenance and adjuvant trials (adding a pill or nothing). Unblinding at interim analysis, or effective unblinding through side effects (alopecia, rash), can compromise a trial, and open-label designs tend to show larger investigator-assessed PFS effects than blinded review.

## Fields

- Kind: Term
- Last checked: 2026-09-09
- Also known as: double-blind; double blind; double-blinded; blinded; open-label; open label; unblinded; placebo-controlled; placebo-controlled trial; matching placebo; single-blind; investigator-blinded; assessor-blinded; blinded assessment; blinded independent review; unblinding

## Sources

- Wikipedia: https://en.wikipedia.org/wiki/Blinded_experiment
- Wikipedia: https://en.wikipedia.org/wiki/Blinded_experiment

## Connected records

- terms: [Blinded independent central review (BICR)](https://onco.cc/terms/bicr/), [Blinded trial](https://onco.cc/terms/blinding/), [Clinical equipoise](https://onco.cc/terms/clinical-equipoise/), [Control arm and comparator (investigator's choice)](https://onco.cc/terms/control-arm/), [Intention-to-treat (ITT) and per-protocol analysis](https://onco.cc/terms/intention-to-treat/), [N-of-1 trial](https://onco.cc/terms/n-of-1-trial/), [Placebo](https://onco.cc/terms/placebo/), [Single-arm trial](https://onco.cc/terms/single-arm/), [Stratified randomisation, allocation concealment and minimisation](https://onco.cc/terms/stratified-randomisation/)
- fronts: [Drug Discovery Platforms](https://onco.cc/fronts/drug-discovery/)
- trials: [ACT IV](https://onco.cc/trials/act-iv/), [Add-Aspirin](https://onco.cc/trials/add-aspirin/), [KEYNOTE-564](https://onco.cc/trials/keynote-564/), [Low-dose olanzapine for cancer anorexia (Tata Memorial)](https://onco.cc/trials/olanzapine-appetite-tmh/)

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