title: Late divergence of survival curves in cancer immunotherapy trials: interpretation and implications.
abstract: Late divergence of survival curves of treated patients and controls is commonly seen in successful cancer immunotherapy trials. Although late survival curve divergence may be caused by a delayed action of therapy, it may also be related to early effects of the treatment. We suggest that late survival divergence most often reflects a specific benefit of therapy for patients who suffer from a comparatively slow progression of disease. The occurrence of delayed survival curve divergence has important implications for the statistical analysis of immunotherapy trials. Thus, it leads to non-proportional hazard ratios that make commonly used statistical tests, e.g., the logrank test, suboptimal. It is therefore suggested that the statistical analysis of immunotherapy trials primarily should be based on a test that compares the survival curves at or after a prespecified, fixed, late time point.
authors: Sahlgrenska Cancer Center, University of Gothenburg, Box 425, 405 30, Göteborg, Sweden, fredrik.thoren@gu.se.
authors: Fredrik B
authors: FB
authors: Thorén
authors: Harald
authors: H
authors: Anderson
authors: Örjan
authors: Ö
authors: Strannegård
mesh_terms: D016022:Case-Control Studies; D006801:Humans; D007167:Immunotherapy; D053208:Kaplan-Meier Estimate; D015233:Models, Statistical; D009369:Neoplasms / Q000276:immunology / Q000401:mortality* / Q000628:therapy*; D016896:Treatment Outcome
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