Primary, secondary and co-primary endpoints

Common oncology primary endpoints are overall survival, progression-free survival (often by blinded central review), event-free or disease-free survival, objective response rate, and pathological complete response; dual or co-primary endpoints (PFS and OS) split the type I error between them with hierarchical testing. A trial that misses its primary but shows a survival trend is 'technically negative' (BILCAP, JAVELIN Ovarian) and regulators rarely approve on secondary endpoints alone. Endpoint choice shapes approval speed (surrogates are faster) and interpretation, and changing the primary endpoint mid-trial, or reporting a secondary as if it were primary, are recognised warning signs.