# Placebo

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

## TL;DR

An inactive look-alike treatment given to the comparison group in a trial so that neither patients nor doctors can tell who is on the real drug. In cancer trials it is added on top of standard treatment, never given instead of it.

## Summary

Placebos control for the placebo effect (improvement from expectation), for the extra attention trial patients receive, and for bias in how symptoms and side effects are reported; in oncology a placebo arm nearly always means 'standard of care plus placebo' versus 'standard of care plus new drug', since withholding effective treatment would be unethical. Placebo-controlled designs are most common in adjuvant and maintenance settings where the comparator is observation, and they are impossible when the new drug's side effects give it away. When an active standard exists, trials compare against it directly (open-label or double-dummy) rather than using placebo.

## Fields

- Kind: Term
- Last checked: 2026-09-09
- Also known as: placebos; placebo-controlled; placebo controlled; placebo arm; placebo group; dummy pill; sugar pill; placebo effect; sham

## Sources

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

## Connected records

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