The additive role of diffusion-weighted magnetic resonance imaging to axillary nodal status evaluation in cases of newly diagnosed breast cancer

Background: Axillary nodal status is crucial for the management of cases with recently diagnosed breast cancer; usually addressed via axillary ultrasonography (US) along with tissue sampling in case of suspicion. Axillary nodal dissection and sentinel biopsy may be done, but are rather invasive, carrying a potential complication risk, which raises the need for non-invasive, reliable, pre-operative axillary imaging. We aimed at evaluating the performance of diffusion-weighted imaging (DWI) regarding preoperative axillary evaluation, using functional information derived from diffusion capacity differences between benign and malignant tissue. We included 77 axillary nodes from 77 patients (age range 20-78 years, mean 50 +/- 12.6 SD) in our prospective study, presenting with variable clinical breast complaints, all scoring BIRADS 4/5 on sonomammography (SM). They underwent axillary evaluation by both US and DW-MRI where US classified nodes into benign, indeterminate, or malignant by evaluating nodal size, shape, cortical thickness, and hilar fat. Qualitative DWI classified them into either restricted or not and a cut-off apparent diffusion coefficient (ADC) value was calculated to differentiate benign and malignant nodal involvement. Results for each modality were correlated to those of final histopathology, which served as the standard of reference. Results: The calculated sensitivity, specificity, accuracy, PPV, and NPV for US was 100%, 36.6%, 75.3%, 71.2%, and 100%, respectively. Statistical indices for qualitative DWI were 76.6%, 63.3%, 76.6%, 63.3%, and 71.4%, respectively (P value < 0.001). The calculated cut off value for ADC between infiltrated and non-infiltrated nodes was 0.95 x 10(-3) mm(2)/s concluding statistical indices of 76.6%, 63.3%, 76.6%, 63.3%, and 71.4%, respectively (P value < 0.001). Conclusion: Combining DW-MRI to conventional US improves diagnostic specificity and overall accuracy of preoperative axillary evaluation of patients with recently discovered breast cancer.