|The following article features coverage from the 2019 San Antonio Breast Cancer Symposium. Click here to read more of Cancer Therapy Advisor‘s conference coverage.|
Pathologists in the real world may be assigning the wrong immune-cell score with PD-L1 assays to patients, which can lead to inappropriate treatment recommendations. The study findings were presented during a poster discussion at the 2019 San Antonio Breast Cancer Symposium (SABCS) in San Antonio, Texas.1
A total of 19 pathologists from 14 institutions were digitally sent stained slides for triple-negative breast cancer specimens and asked to score the samples as PD-L1 positive (≥ 1% immune cell staining) or negative (< 1% immune cell staining) and estimate the percentage of immune cell staining for positive samples. Specimens were stained using 2 PD-L1 expression assays from Ventana, SP142 and SP263, and a total of 68 slides for SP142 and 76 for SP263 were digitally sent to pathologists.
The Ventana PD-L1 (SP142) assay is approved by the US Food and Drug Administration to determine which patients with locally advanced or metastatic triple-negative breast cancer have tumors that express PD-L1 and can therefore receive atezolizumab.2
Pathologists interpreted the stain as PD-L1–positive for 78% of samples (range, 64% – 96%) with the SP263 assay and 58% (range, 41% – 81%) with the SP142 assay (P <.0001). Pathologists were in complete agreement for only 50% of samples with SP263 and 38% of samples with SP142, yielding an intraclass correlation coefficient of 0.513 for SP263 and 0.560 for SP142.
In addition, the researchers created a new method called Observers Needed to Evaluate Subjective Tests (ONEST). Using this, they found the overall percentage agreement appeared to plateau at 46% with 10 pathologists for SP263 and 41% with 9 pathologists for SP142.
“With that overall percentage agreement at 40%, it suggests that over half of pathologists in real-world situations could be misaligning the patient immune cell score,” said poster discussant Ashley Cimino-Mathews, MD, associate professor of pathology and oncology at the Johns Hopkins University School of Medicine in Baltimore, Maryland.
Disclosure: Some authors of this study disclosed financial relationships with the pharmaceutical industry. For a full list of disclosures, please refer to the original abstract.
Read more of Cancer Therapy Advisor‘s coverage of SABCS by visiting the conference page.
- Reisenbichler ES, Han G, Pelekanou V, et al. Prospective multi-institutional evaluation of pathologist assessment of PD-L1 assays in triple negative breast cancer. Poster presentation at: 2019 San Antonio Breast Cancer Symposium; December 10-14, 2019; San Antonio, TX. Abstract PD5-01.
- FDA approves atezolizumab for PD-L1 positive unresectable locally advanced or metastatic triple-negative breast cancer [news release]. Silver Spring, MD: U.S. Food and Drug Administration; March 8, 2019. https://www.fda.gov/drugs/drug-approvals-and-databases/fda-approves-atezolizumab-pd-l1-positive-unresectable-locally-advanced-or-metastatic-triple-negative. Accessed December 10, 2019.