Variability in Breast Cancer Biomarker Assessment and the Effect on Oncological Treatment Decisions: A Nationwide 5-Year Population-Based Study
Department of Oncology and Pathology, Karolinska Institutet, 17176 Stockholm, Sweden
Department of Clinical Pathology and Cytology, Karolinska University Laboratory, 11883 Stockholm, Sweden
Department of Breast, Endocrine Tumors and Sarcoma, Karolinska University Hospital, 17176 Stockholm, Sweden
Department of Molecular Medicine and Surgery, Karolinska Institutet, 17176 Stockholm, Sweden
Division of Clinical Genetics, Department of Laboratory Medicine, Lund University, 22185 Lund, Sweden
Division of Oncology and Pathology, Department of Clinical Sciences Lund, Lund University, 22184 Lund, Sweden
Department of Clinical Pathology, Sahlgrenska University Hospital, 41345 Gothenburg, Sweden
Department of Clinical Medicine, Aalborg University, 9000 Aalborg, Denmark
NordiQC, Institute of Pathology, Aalborg University Hospital, 9000 Aalborg, Denmark
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
Revised: 24 February 2021
Accepted: 26 February 2021
Published: 9 March 2021
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.