Influence of Mammographic Density on the Diagnostic Accuracy of Tumor Size Assessment and Association with Breast Cancer Tumor Characteristics

Purpose The accuracy of breast cancer staging involves the estimation of the tumor size for the initial treatment decision. We investigated the accuracy of tumor size estimation and the association between tumor characteristics and breast density (BD). Materials and Methods A total of 434 women with the diagnosis of primary breast cancer were included in this prospective study at the University Breast Center Franken (UBF). Estimated tumor characteristics included tumor size, nodal status, estrogen/progesterone receptor status, Ki-67, HER2/neu, vascular or lymphatic invasion. Radiomorphological data included tumor size as assessed by mammography, breast ultrasonography, and clinical examination, and American College of Radiology (ACR) categories for BD. Results BD did not have a significant impact on the assessment of tumor size using breast ultrasound (deviation from ACR categories 1–4: 0.55–0.68 cm; P=0.331). The deviation in mammography was significantly different dependent on BD (0.42–0.9 cm; P <0.001). The clinical examination was not affected by BD. Age and tumor size were the only parameters associated with a denser breast in the multivariate analysis. Older women were less likely to have dense breasts (odds ratio 0.157 for women aged >70 years), and patients with larger tumors were less likely to have dense breasts (OR 0.36 for tumors >2 cm). Conclusion Breast ultrasonography is more accurate than mammography for assessing tumor size in breasts with a higher BD. The difference in tumor size assessment needs to be taken into consideration in the design of clinical trials and treatment decisions.