Assessment of axillary lymph nodes in patients with breast cancer with diffusion-weighted MR imaging in combination with routine and dynamic contrast MR imaging.

Abstract

To assess axillary lymph nodes in patients with breast cancer with diffusion-weighted MR imaging in combination with routine and dynamic contrast MR imaging. Prospective study was conducted on 65 enlarged axillary lymph nodes in 34 consecutive female patients (28-64 years: mean 51 years) with breast cancer. They underwent T2-weighted, dynamic contrast-enhanced and diffusion-weighted MR imaging of the breast and axilla using a single-shot echo-planar imaging with a b factor of 0500 and 1000 s/mm². Morphologic and quantitative parameters included ADC value of the axillary lymph node which was calculated and correlated with surgical findings. The mean ADC value of metastatic axillary lymph nodes was 1.08 ± 0.21 × 10⁻³ mm²/s and of benign lymph nodes was 1.58 ± 0.14 × 10⁻³ mm²s. There was statistically difference in mean ADC values between metastatic and of benign axillary lymph nodes (P = 0.001). Metastatic nodes were associated with low ADC ≤ 1.3 (OR = 8.0), short axis/long axis (TS/LS) > 0.6 (OR = 7.0) and absent hilum (OR = 6.21). When ADC of 1.3 × 10⁻³ mm²/s was used as a threshold value for differentiating metastatic from benign axillary lymph nodes, the best result was obtained with an accuracy of 95.6%, sensitivity of 93%, specificity of 100%, positive predictive value of 100 %, negative predictive value of 87.5 % and area under the curve of 0.974. Multivariate model involving combined ADC value and TS/LS improved the diagnostic performance of MR imaging with AUC of 1.00. We concluded that combination of diffusion-weighted MR imaging with morphological and dynamic MR imaging findings helps for differentiation of metastatic from benign axillary lymph nodes.