Accuracy of tumour size assessment in the preoperative staging of breast cancer: comparison of digital mammography, tomosynthesis, ultrasound and MRI

Accurate measurement of breast tumour size is fundamental for treatment planning. We compared the accuracy of digital mammography (DM), digital breast tomosynthesis (DBT), ultrasound (US) and magnetic resonance imaging (MRI) for the preoperative evaluation of breast cancer size. We retrospectively reviewed 149 breast cancers in 110 patients who underwent DM, DBT, US and MRI between January 2010 and December 2011, before definitive surgery. The lesions were measured by two radiologists, without knowledge of the final histological examination, considered the gold standard. For each imaging modality, the maximum tumour size was measured to the nearest millimetre; the measurements were considered concordant if they were within +/- 5 mm. Pearson's correlation coefficient was calculated for each imaging modality. The median pathological tumour size was 22.3 mm. MRI and DBT had a level of concordance with pathology of 70% and 66%, respectively, which was higher than that of DM (54%). DBT and MRI measurements had a better correlation with pathological tumour size (R:0.89 and R:0.92, respectively) compared to DM (R:0.83) and US (R:0.77). DBT and MRI are superior to DM and US in the preoperative assessment of breast tumour size. DBT seems to improve the accuracy of DM, although MRI remains the most accurate imaging modality for breast cancer extension.