Abstract 5307: The impact of image analysis and multiplex hybridization on PD-L1 diagnostic case triage

Abstract

Abstract Introduction: Immune checkpoint blockade therapy is a new paradigm in cancer treatment with durable tumor regression and prolonged stabilization of disease in patients with advanced cancers, including non-small cell lung cancer (NSCLC). However, clinical assessment using immunohistochemistry (IHC) remains complex and ambiguous. Methods: PD-L1 IHC staining was performed as a routine clinical reflex test on 802 NSCLC cases over an 18 month period using an automated staining system with PD-L1 clone SP263. PD-L1 expression was assessed using image analysis (IA) by 2 individuals and concordance was evaluated between the recorded manual clinical score and the digitally generated score. Additionally, a subset of 330 samples, representing cases with either varying PD-L1 expression or difficulty in assessment, were stained by multiplex immunofluorescence. Sensitivity and specificity was compared between manual assessments of both chromogenic and multiplex IHC. Results: PD-L1 expression by IA showed significant concordance (R²=0.8248) to manual assessment. Sensitivity and specificity was 86.8% and 91.4%, respectively. Discordant cases were mainly due to spurious or poor staining quality, difficult classification by IA and overabundant macrophages and a low IA detection threshold. Evaluation of IA scores 10-49% and >70% revealed 96.8% concordance to manual assessment. Multiplex assessment enabled PD-L1+/CD68+ macrophages to be readily identified within PD-L1+/CK+ or PD-L1-/CK+ tumor nests. Manual assessment of multiplex vs. chromogenic IHC was highly concordant, with a sensitivity and specificity respectively of 97.8% and 91.8%. Conclusions: Deployment of IA in routine PD-L1 IHC assessment of NSCLC represents a beneficial time saving process and could aid case triage saving >50% of pathologist review time. However cases close to diagnostic thresholds still require a more comprehensive pathological evaluation. Multiplex IHC provides a higher level of confidence in PD-L1 assessment and could be offered for challenging cases by centers with access to appropriate expertise and specialist equipment. Citation Format: Matthew P. Humphries, Victoria Bingham, Fatima Abdullahi Sidi, Stephanie G. Craig, Stephen McQuaid, Jacquline James, Manuel Salto-Tellez. The impact of image analysis and multiplex hybridization on PD-L1 diagnostic case triage [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 5307.