PD-L1 Expression Scoring: Non-Interchangeable, Non-Interpretable, Neither, or Both
Menée à partir d'échantillons tumoraux prélevés sur 614 patientes atteintes d'un cancer du sein triple négatif de stade avancé et incluses dans un essai de phase III évaluant l'atézolizumab en combinaison avec le nab-paclitaxel, cette étude analyse la concordance des résultats de trois tests immunohistochimiques destinés à déterminer le statut PD-L1 des cellules tumorales et des cellules immunitaires ayant infiltré la tumeur
The IMpassion 130 trial led to the approval of anti-PD-L1 agent atezolizumab incombination with nab-paclitaxel as first-line treatment for unresectable locally advanced or metastatic triple-negative breast cancer [1]. Schmid and colleagues showed improved progression free median survival (PFS) by 2 months (hazard ratio [HR] = 0.63; 95% confidence interval [CI] = 0.50–0.80) and most importantly prolonged median overall survival (OS) by 7 months (HR = 0.71; 95% CI = 0.54-0.94) among patients with immune cell (IC) PD-L1 expression ≥ 1% (i.e. IC ≥ 1%). This led to US Food and Drug Administration approval and widespread use of this therapy. The atezolizumab label specifies the use of the Ventana PD-L1 SP142 immunohistochemical (IHC) assay (SP142) where only patients with “IC>1%” are qualified for the drug. This biomarker requirement has opened Pandora’s box since: 1) it is the stipulated IHC assay but has been proven to be less sensitive than other PD-L1 detection assays, 2) it uses a different system for pathologist-based analysis, and 3) since it is not equivalent to other
assays that have subsequently been approved in the same class [2] , it requires the pathologist to know which treatment will be chosen prior to performing the assay (or to perform two unstandardized assays for the same biomarker)
Journal of the National Cancer Institute , éditorial en libre accès, 2020