OnCo
termsTerm

Surrogate endpoint

aka surrogate endpoints, surrogate, surrogates, surrogate marker, surrogate markers, surrogate outcome, intermediate endpoint, intermediate endpoints

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.

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 many 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 When a surrogate-based approval is not confirmed by later survival data, the approval can be withdrawn, as has happened repeatedly since 2021.

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Clinic basics

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