Validation of the QR1 Antibody for the Evaluation of PD-L1 Expression in Non–Small Cell Lung Adenocarcinomas

Abstract

The evaluation of Programmed cell Death Ligand 1 (PD-L1) expression in the tumor cells with immunohistochemistry is a mandatory diagnostic step in the treatment of lung cancer. It is important to utilize validated antibodies that can reliably detect PD-L1 positive cells. Different antibodies have already been studied. In this present study, we compared a new clone (QR1, Quartett) with reference clones to determine if it can be used in place of previously identified reference clones. We built a tissue micro array (TMA) from 110 lung adenocarcinomas and compared it using immunohistodetection of four different clones: QR1, 22c3, Sp263, and E1L3N. We analyzed the correlation between the sample duplicates for each clone and then a correlation and the concordance between the clones were calculated. A total of 101 patients were exploitable; the duplicates for each clone had a strong correlation. The correlation was the strongest (r=0.82) between QR1 and 22c3 and less strong with the other clones. Totals of 78%, 79%, and 97% of the QR1 cases were concordant with 22c3 for the thresholds of <1%, 1% to 49%, and ≥50%, respectively. The sensitivities and specificities of QR1, compared with 22c3, were >75% and 81%, respectively. PD-L1 expression, analyzed in lung adenocarcinomas with QR1, is highly correlated and concordant with the main reference clone used in most laboratories (22c3). It can be used to replace the latter in clinical routine.

Selected highlights of the 2019 Pulmonary Pathology Society Biennial Meeting: PD-L1 test harmonization studies

“…An LDT differs from a clinically-validated and standardized assay by its reagents (primary clone, detection kits), the platform used or the protocol integrating different methods of antigen retrieving, detection or amplification. These tests have been frequently developed with the concentrated antibodies used in the assays (clones 22C3 and 28-8) or with other monoclonal antibodies not used in the assays, in particular the clone E1L3N (validated for research use only -RUO) or the clone QR1 (CE-IVD labeled) (44). More rarely, LDT have been set up with pre-diluted antibodies recovered from PD-L1 assays, to be used on non-dedicated platforms such as Leica Bond IHC platforms.…”