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William J. Gradishar, MD, FACP, FASCO


Triple-Negative Breast Cancer: Are All PD-L1 Assays Created Equal?

By: Joshua Swore, PhD
Posted: Monday, January 22, 2024

Findings published in the journal Breast Cancer Research suggest that SP142 and 22C3 immunohistochemistry assays cannot be used equivalently to detect PD-L1 and to predict outcomes in patients with triple-negative breast cancer. “We investigated the agreement between the SP142 and 22C3 assays in the context of their clinically used scoring systems in triple-negative breast cancer, assessed their correlation to PD-L1 expression at the mRNA level to investigate if the assays differ in their association with the mRNA status, and evaluated their prognostic value in a population-based, early-stage, triple-negative breast cancer cohort,” said Emma Niméus, MD, PhD, of Lund University, Sweden and colleagues. 

A final cohort of 232 patients with triple-negative breast cancer was the focus of the study. Tumor samples were taken from all patients and subjected to both SP142 and 22C3 immunoassays. The investigators used both combined positive scoring and staining in immune cells to assess the results of the immunoassays. Staining of immune cells was given a threshold of 1%, and the combined positive scoring was given thresholds of 1 or 10.

The authors reported expression rates of PD-L1 for the SP142 assay using immune cell staining ≥ 1% at 50.9%. The 22C3 assay yielded expression rates of 27.2% using the combined positive scoring of  ≥ 10, 53.9% for the combined positive scoring of  ≥ 1, and 41.8% using the immune cell staining ≥ 1% scoring system. Concordance analysis was used to identify any independent populations between scoring systems. Concordance values between the SP142 assay and the three different 22C3 scores were 73.7%, 81.5%, and 86.6%, respectively. The score indicated weak agreement between scoring systems and emphasized the importance of using both assays to identify patients with triple-negative breast cancer.

Disclosure: For full disclosures of the study authors, visit

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