J Thorac Oncol. 2021 Mar 1:S1556-0864(21)01732-9. doi: 10.1016/j.jtho.2020.12.026. Online ahead of print.
BACKGROUND: PD-L1 immunohistochemistry (IHC) is required to determine eligibility for pembrolizumab monotherapy in advanced non-small cell lung cancer (NSCLC) worldwide and for several other indications depending on the country. Four assays have been approved/CE-IVD marked, but PD-L1 IHC seems diversely implemented across regions and laboratories with the application of laboratory-developed tests (LDTs).
METHOD: To assess practice of PD-L1 IHC and identify issues and disparities, the IASLC pathology committee conducted a global survey for pathologists from January to May 2019, comprising multiple questions on pre-analytical, analytical and post-analytical conditions.
RESULT: 344 pathologists from 64 countries participated with 41% from Europe, 24% from North America, and 18% from Asia. Besides biopsies and resections, cellblocks were used by 75% of the participants and smears by 11%. The clone 22C3 was most commonly used (69%) followed by SP263 (51%). They were applied as a LDT by 40% and 30% of the users, respectively, and 76% of the participants developed at least one LDT. A half of the participants reported turnaround time (TAT) of ≤ 2 days, while 13% reported that of ≥ 5 days. Additionally, quality assurance (QA), formal training for scoring and standardized reporting were not implemented by 18%, 16% and 14% of the participants, respectively.
CONCLUSION: Heterogeneity in PD-L1 testing is marked across regions and laboratories in terms of antibody clones, IHC assays, samples, TATs and QA measures. The lack of QA, formal training and standardized reporting stated by a significant minority identifies a need for additional QA measures and training opportunities.