Apparent diffusion coefficient magnetic resonance imaging (ADC-MRI) in the axillary breast cancer lymph node metastasis detection: a narrative review

Abstract

The presence of axillary lymph nodes metastases in breast cancer is the most significant prognostic factor, with a great impact on morbidity, disease-related survival and management of oncological therapies; for this reason, adequate imaging evaluation is strictly necessary. Physical examination is not enough sensitive to assess breast cancer nodal status; axillary ultrasonography (US) is commonly used to detect suspected or occult nodal metastasis, providing exclusively morphological evaluation, with low sensitivity and positive predictive value. Currently, sentinel lymph node biopsy (SLNB) and/or axillary dissection are the milestone for the diagnostic assessment of axillary lymph node metastases, although its related morbidity. The impact of magnetic resonance imaging (MRI) in the detection of nodal metastases has been widely investigated, as it continues to represent the most promising imaging modality in the breast cancer management. In particular, diffusion-weighted imaging (DWI) and apparent diffusion coefficient (ADC) values represent additional reliable non-contrast sequences, able to improve the diagnostic accuracy of breast cancer MRI evaluation. Several studies largely demonstrated the usefulness of implementing DWI/ADC MRI in the characterization of breast lesions. Herein, in the light of our clinical experience, we perform a review of the literature regarding the diagnostic performance and accuracy of ADC value as potential pre-operative tool to define metastatic involvement of nodal structures in breast cancer patients. For the purpose of this review, PubMed, Web of Science, and SCOPUS electronic databases were searched with different combinations of "axillary lymph node", "breast cancer", "MRI/ADC", "breast MRI" keywords. All original articles, reviews and metanalyses were included.

Keywords: Breast cancer; apparent diffusion coefficient magnetic resonance imaging (ADC-MRI); axillary lymph nodes; diffusion-weighted imaging (DWI); metastases.

Figure 1

ADC values of metastatic and non-metastatic lymph nodes. ADC values of metastatic lymph nodes were significantly lower than those of non-metastatic lymph nodes (P<0.001). ADC, apparent diffusion coefficient.

Figure 2

The area under the ROC curve was 0,876. Using an ADC cut-off value of 0.8×10⁻³ mm²/s, sensitivity and specificity for diagnosing metastatic axillary lymph node were 82.6% and 86% respectively. ROC, receiver operating characteristic; ADC, apparent diffusion coefficient.

Figure 3

Graphical representation of ADC cut-off value and related specificity and sensitivity. ADC, apparent diffusion coefficient.

Figure 4

MRI images in patient with breast cancer and metastatic lymph nodes. (A) Axial T2-weighted fat suppression image for the localisation of the lymph node under analysis; (B) ADC map with three ROI positioning; ADC value is obtained by the mean of three measured values. MRI, magnetic resonance imaging; ADC, apparent diffusion coefficient; ROI, region of interest.

Figure 5

MRI images of a patient with breast carcinoma and benign lymph nodes. (A) Axial T2-weighted fat suppression image for the localisation of the lymph node under analysis; (B) ADC map with three ROI positioning; ADC value is obtained by the mean of three measured values. MRI, magnetic resonance imaging; ADC, apparent diffusion coefficient; ROI, region of interest.