# Surrogate endpoint

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

## TL;DR

A quicker, easier measurement used as a stand-in for what really matters. Tumour shrinkage or delayed growth stands in for living longer, on the assumption, not always true, that one leads to the other.

## Summary

Progression-free survival, response rate, pathologic complete response, minimal residual disease and ctDNA clearance are the main surrogates in oncology; they are available months or years before overall survival and need fewer patients, so they drive most accelerated approvals and a share of full ones. A surrogate is valid for a given drug class and disease only if trials show that improving it reliably improves survival, and this correlation is strong in some settings (PFS in ovarian cancer maintenance) and weak in others (response rate in many solid tumours). When a surrogate-based approval is not confirmed by later survival data, the approval can be withdrawn, as has happened repeatedly since 2021.

## Fields

- Kind: Term
- Last checked: 2026-09-09
- Also known as: surrogate endpoints; surrogate; surrogates; surrogate marker; surrogate markers; surrogate outcome; intermediate endpoint; intermediate endpoints; surrogate for survival; validated surrogate; intermediate clinical endpoint; early endpoint; reasonably likely to predict clinical benefit; trial-level surrogacy; patient-level surrogacy; surrogacy; surrogate-endpoint-term

## Sources

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

## Connected records

- terms: [Accelerated approval](https://onco.cc/terms/accelerated-approval/), [AMNOG (Germany, 2011)](https://onco.cc/terms/amnog/), [Confirmatory trial](https://onco.cc/terms/confirmatory-trial/), [Crossover in trials](https://onco.cc/terms/crossover/), [Endpoint](https://onco.cc/terms/endpoint/), [Event-free / disease-free survival (EFS, DFS, iDFS, RFS)](https://onco.cc/terms/efs/), [FDORA 2022 accelerated approval reforms](https://onco.cc/terms/fdora-2022/), [Minimal / molecular residual disease (MRD)](https://onco.cc/terms/mrd/), [Objective response rate (ORR)](https://onco.cc/terms/orr/), [Overall survival (OS)](https://onco.cc/terms/os/), [Partial response](https://onco.cc/terms/partial-response/), [Pathologic complete response (pCR)](https://onco.cc/terms/pcr/), [Phase 1, 2 and 3 trials](https://onco.cc/terms/trial-phases/), [Primary, secondary and co-primary endpoints](https://onco.cc/terms/primary-endpoint/), [Progression-free survival (PFS)](https://onco.cc/terms/pfs/), [Stage shift](https://onco.cc/terms/stage-shift/), [Surrogate endpoint validation: which stand-ins have earned trust](https://onco.cc/terms/surrogate-validation/), [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: [ANNOUNCE](https://onco.cc/trials/announce/), [KEYNOTE-522](https://onco.cc/trials/keynote-522/), [TROPION-Breast01](https://onco.cc/trials/tropion-breast01/), [UKCTOCS](https://onco.cc/trials/ukctocs/)
- journals: [JAMA Internal Medicine](https://onco.cc/journals/jama-internal-medicine/)
- roadmaps: [Trial modernisation roadmap: the randomised trial → platforms and adaptive designs → decentralised, pragmatic and always-on](https://onco.cc/roadmaps/trial-modernisation-roadmap/)

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JSON: https://onco.cc/api/v1/entities/surrogate-endpoint.json