Discordance between PAM50 intrinsic subtyping and immunohistochemistry in South African women with breast cancer

Purpose Breast cancer is a heterogeneous disease with different gene expression profiles, treatment options and outcomes. In South Africa, tumors are classified using immunohistochemistry. In high-income countries multiparameter genomic assays are being utilized with implications for tumor classific...

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Published in:Breast cancer research and treatment Vol. 199; no. 1; pp. 1 - 12
Main Authors: Dix-Peek, Thérèse, Phakathi, Boitumelo P., van den Berg, Eunice J., Dickens, Caroline, Augustine, Tanya N., Cubasch, Herbert, Neugut, Alfred I., Jacobson, Judith S., Joffe, Maureen, Ruff, Paul, Duarte, Raquel A. B.
Format: Journal Article
Language:English
Published: New York Springer US 01.05.2023
Springer
Springer Nature B.V
Subjects:
Biomarkers, Tumor - genetics
Biomarkers, Tumor - metabolism
Breast cancer
Breast Neoplasms - pathology
Cancer research
Care and treatment
Discordance
ErbB-2 protein
Female
Gene expression
Genes
Genomics
Humans
Immunohistochemistry
Ki-67 Antigen - genetics
Medical research
Medicine
Medicine & Public Health
Medicine, Experimental
Oncology
Patients
Preclinical Study
Receptor, ErbB-2 - genetics
Receptor, ErbB-2 - metabolism
Receptors, Progesterone - genetics
Receptors, Progesterone - metabolism
South Africa - epidemiology
Tumors
Women
South Africa
Immunohistochemistry
PAM50
Subtypes
Breast cancer
Sub-Saharan Africa
ISSN:0167-6806, 1573-7217, 1573-7217
Online Access:Get full text
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Summary:Purpose Breast cancer is a heterogeneous disease with different gene expression profiles, treatment options and outcomes. In South Africa, tumors are classified using immunohistochemistry. In high-income countries multiparameter genomic assays are being utilized with implications for tumor classification and treatment. Methods In a cohort of 378 breast cancer patients from the SABCHO study, we investigated the concordance between tumor samples classified by IHC and the PAM50 gene assay. Results IHC classified patients as ER-positive (77.5%), PR-positive (70.6%), and HER2-positive (32.3%). These results, together with Ki67, were used as surrogates for intrinsic subtyping, and showed 6.9% IHC-A-clinical, 72.7% IHC-B-clinical, 5.3% IHC-HER2-clinical and 15.1% triple negative cancer (TNC). Typing using the PAM50 gave 19.3% luminal-A, 32.5% luminal-B, 23.5% HER2-enriched and 24.6% basal-like. The basal-like and TNC had the highest concordance, while the luminal-A and IHC-A group had the lowest concordance. By altering the cutoff for Ki67, and realigning the HER2/ER/PR-positive patients to IHC-HER2, we improved concordance with the intrinsic subtypes. Conclusion We suggest that the Ki67 be changed to a cutoff of 20–25% in our population to better reflect the luminal subtype classifications. This change would inform treatment options for breast cancer patients in settings where genomic assays are unaffordable.
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ISSN:0167-6806
1573-7217
1573-7217
DOI:10.1007/s10549-023-06886-3