Evaluation of tumor extent in breast cancer patients using real-time MR navigated ultrasound: preliminary study

Objectives: To evaluate the accuracy of real-time MR navigated ultrasound (MRnav US) for tumor extent measurements in breast cancer and to investigate variables influencing the accuracy of MRnav US in comparison with US alone.

Methods: Fifty-three patients with 60 malignancies underwent preoperative breast MRI and US with or without MRI navigation. Maximum lesion sizes based on MRnav US and US alone were measured, and their relationship with the pathology was analyzed considering the differences in the clinicopathologic variables of the patients.

Results: Among 60 breast cancers, mean lesion size at initial breast US without MRI navigation and at MRI-navigated US was 19 mm and 24 mm, respectively, compared with 28 mm on the histopathology. Overall, the tumor size estimated with MRnav US was more strongly correlated with the histologic tumor size than with US alone. Accurate measurements by MRnav US were significantly more frequent in the lesions that were presented as a mass type on MRI. In addition, the accurate measurement of mass extent was improved with MRnav US in patients who had non-mass type lesions on MRI and who had undergone neoadjuvant systemic chemotherapy when compared with US alone.

Conclusion: MRnav US was more accurate for tumor extent estimation than US alone, and specific clinicopathologic variables can affect the accuracy of MRnav US.