2023PEvaluating the prevalence of the expression of PD-L1 in NSCLC specimens with short-duration formalin fixation using IHC 22C3 pharmDx

Abstract Background Immune checkpoint inhibitors mediated by PD-1 and PD-L1 are promising treatments for various tumors. The PD-L1 expression in tumor cells was found to be correlated with the likelihood of a response to PD-1- or PD-L1-targeted therapy in non-small cell lung cancer (NSCLC). For PD-L1 immunohistochemistry (IHC), 22C3 pharmDx is the only companion diagnostic assay that can identify NSCLC patients suitable for pembrolizumab treatment. Specimens are scored and divided into 3 categories ( Methods We screened consecutive NSCLC patients who underwent tumor biopsy by bronchoscopy between January 2017 and June 2018 at National Hospital Organization Fukuokahigashi Medical Center. In the present study, we only included 70 patients whose tumors were formalin-fixed for less than 6 h and whose PD-L1 expression had been evaluated by IHC with antibodies to human PD-L1 (22C3 pharmDx). Results The PD-L1 prevalence in patients with NSCLC in our hospital was 26 (37%) with TPS Conclusions The PD-L1 prevalence in specimens with short-duration formalin fixation was consistent with the results of the KEYNOTE-024 trial. We will present our conclusion regarding these results, including the characteristics of patients and the PD-L1 prevalence in specimens fixed for 12-72 h in our institution, from July 2018 onward. Legal entity responsible for the study National Hospital Organization Fukuokahigashi Medical Center. Funding JSPS KAKENHI JP18K15927. Disclosure All authors have declared no conflicts of interest.