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Diagnostic delay is more frequent in triple negative breast cancer than in hormone receptor-positive breast cancer
Baumgartner S.1, Güth U.2, Reeve K.3, Elfgen C.2
1Universität Zürich, Frauenklinik, Zürich, Schweiz, 2Brust-Zentrum AG Zürich, Zürich, Schweiz, 3Universität Zürich, Epidemiology, Biostatistics and Prevention Institute, Biostatistics Departement, Zürich, Schweiz

Background: Triple negative breast cancer (TNBC) are aggressive types of breast cancer with poor prognosis. Previous studies imply that TNBC more often present a benign appearance in clinical imaging than other types of breast cancer. This study aims to explore misdiagnosis in clinical imaging and diagnostic delay as a possible consequence.
Methods: In a single-center study, diagnostic process of breast cancer patients with TNBC or Hormone receptor-positive breast cancer (HR+) was retrospectively analyzed regarding to diagnostic delay; which was defined as one month or more. All patients received a mammogram and a breast ultrasound in clinical routine.
Results: A total of 782 patients with either TNBC (n=157) or HR+ (n=605) were included. Overall, 36 patients (4.7%) experienced a diagnostic delay. Delay was significant more frequent in patients with TNBC (9.6%) than in patients with HR+ (3.5%), leading to a tumor stage upgrade most cases (58.3%). Diagnostic delay mainly based on benign BIRADS-classifications in mammogram and/or ultrasound.
Patients who experienced a delay tend to have a smaller tumor and are at younger age. The unadjusted odds ratio for delay risk in TNBC patients compared to HR+ patients is 2.94, indicating an increased risk of diagnostic delay in TNBC patients (p-value=0.002).
Conclusion: This study shows a higher risk for diagnostic delay in TNBC patients compared to HR+ patients, based on misclassification due to benign imaging criteria. Delay can lead to a clinically significant tumor growth.