Open AccessArticle
Variability in Breast Cancer Biomarker Assessment and the Effect on Oncological Treatment Decisions: A Nationwide 5-Year Population-Based Study
by
1,2,†
, 3,4,†
, 1,2, 5, 5,6, 7, 8,9
, 1,10 and 1,2,*
1
Department of Oncology and Pathology, Karolinska Institutet, 17176 Stockholm, Sweden
2
Department of Clinical Pathology and Cytology, Karolinska University Laboratory, 11883 Stockholm, Sweden
3
Department of Breast, Endocrine Tumors and Sarcoma, Karolinska University Hospital, 17176 Stockholm, Sweden
4
Department of Molecular Medicine and Surgery, Karolinska Institutet, 17176 Stockholm, Sweden
5
Division of Clinical Genetics, Department of Laboratory Medicine, Lund University, 22185 Lund, Sweden
6
Division of Oncology and Pathology, Department of Clinical Sciences Lund, Lund University, 22184 Lund, Sweden
7
Department of Clinical Pathology, Sahlgrenska University Hospital, 41345 Gothenburg, Sweden
8
Department of Clinical Medicine, Aalborg University, 9000 Aalborg, Denmark
9
NordiQC, Institute of Pathology, Aalborg University Hospital, 9000 Aalborg, Denmark
10
Breast Center, Cancer Theme, Karolinska University Hospital and Karolinska Comprehensive Cancer Center, Gävlegatan 55, 17164 Solna, Sweden
*
Author to whom correspondence should be addressed.
†
These authors contributed equally to this work.
Academic Editor: Rupert Bartsch
Received: 1 January 2021
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Revised: 24 February 2021
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Accepted: 26 February 2021
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Published: 9 March 2021
Simple Summary
Biomarkers that define breast cancer treatment recommendations include estrogen receptor (ER), progesterone receptor (PR), and human epidermal growth-factor receptor 2 (HER2); histological grade; and in many countries, the Ki67 proliferation index. However, the subjective nature and degree of variability in breast cancer biomarker assessment might result in under- or overtreatment. We demonstrated that limited variability exists in ER, PR, and HER2 positivity rates among 29 departments in Sweden, including 43,261 patients. However, even a few outlier labs affect endocrine and anti-HER2 treatment rates in a clinically relevant proportion, indicating a need for improvement. Despite international guidelines, standardized protocols, and external quality control procedures, very high variability was found in Ki67 scoring and histological grading, indicating a need for new methods. Monitoring rates of biomarker expression and treatments among departments should be mandatory in order to detect variability issues affecting the clinical management of breast cancer.