The value of MRI in the detection of axillary lymph node metastases in breast cancer: a systematic review

Staging of the axillary lymph nodes is an essential step to determine the appropriate treatment for breast cancer. Sentinel lymph node biopsy (SLNB) is currently the first step in staging and the gold standard. However, if the sentinel node is positive, a full dissection of the axillary lymph nodes should be performed (axillary lymph node dissection or ALND). This technique used to be the gold standard but had considerable sequelae which diminished quality of life. SLNB still has sequelae but the incidence is much lower. The goal of this systematic review is to assess whether MRI can replace or assist the current gold standard for axillary lymph node staging in breast cancer. With the use of these non-invasive techniques, the risk of morbidity could be reduced even more. A comprehensive search and an additional brief search in several databases has been performed using PRISMA. Studies were selected based on titles and abstracts and were included or excluded using predetermined criteria. The studies were assessed for validity and applicability using the QUADAS-2 tool by two readers. Data of three studies using diffusion-weighted imaging (DWI) were pooled and statistical analysis was performed. A total of seven studies were included for review. Three studies used DWI, others used T2-weighted imaging, contrast-enhanced imaging, T1-weighted imaging or an MRI scoring system. Due to the heterogeneously divided MRI modalities, a small meta-analysis of DWI was performed. Other studies were evaluated qualitatively. DWI reached a sensitivity of 87.67% (95% CI 77.88-94.20) and a specificity of 59.31% (95% CI 50.85-67.38), a positive predictive value (PPV) of 52.03% (95 CI 42.84-61.12), and a negative predictive value (NPV) of 90.53% (95% CI 82.78-95.58). MRI can aid in the detection of axillary lymph node metastasis, but it cannot replace the current gold standard (SLNB/ALND).