Abbreviated MRI for Comprehensive Regional Lymph Node Staging during Pre-Operative Breast MRI

SIMPLE SUMMARY: The clinically relevant information that guides further surgical management of the axilla in women with breast cancer is the distinction between non-significant (N0–N1) versus significant (≥N2) lymph node metastases. In women with newly diagnosed breast cancer, MRI is increasingly used to determine the local extent of disease in the breast. The aim of our retrospective study on 414 patients who underwent routine breast MRI for local staging of the breast was to determine whether an abbreviated protocol for regional lymph node staging is sufficient to identify patients with significant nodal disease. Our results demonstrated that a single 3 min coronal T1-weighted sequence, acquired with the system’s built-in body coil, covering the chest wall, axilla, and supra- and infraclavicular region, helped rule out the presence of significant nodal disease with a NPV of 98.8% [97.0–100%]. False-positive findings were mostly caused by patients with positive, but non-significant, lymph node metastases (N1). ABSTRACT: Background: The detection of regional lymph node metastases (LNM), in particular significant LNM (≥N2), is important to guide treatment decisions in women with breast cancer. The purpose of this study was to determine whether a coronal pulse sequence as part of pre-operative breast MRI is useful to identify women without significant LNM. Material: Retrospective study between January 2017 and December 2019 on 414 consecutive women with breast cancer who underwent pre-operative breast MRI on a 1.5 T system. For lymph node (LN) staging, a coronal pre-contrast non-fat-suppressed T1-weighted TSE sequence was acquired with the system’s built-in body coil, covering the chest wall; acquisition time 3:12 min. Two radiologists rated the likelihood of LNM on a 3-point scale (absent/possible/present). Validation was obtained by histology from sentinel LN biopsy, axillary LN dissection, and/or PET/CT. Results: 368/414 women were staged to have no or non-significant LNM (pN0 in 282/414, pN1 in 86/414), and significant LNM (≥pN2) in 46/414. For identification of women with significant LNM, MRI was true-positive in 42/46, false-negative in 4/46, true-negative in 327/368, and false-positive in 41/83, the latter mostly caused by women with N1-disease (38/41), yielding an NPV and PPV for significant LNM of 98.8% [95%-CI: 97.0–100%] and 50.6% [43.1–58.1%], respectively. Conclusions: A 3 min coronal T1-weighted pulse sequence covering the chest wall as part of pre-operative breast MRI is useful to rule out significant LNM with high NPV. Where MRI staging is positive for significant LNM, additional work-up is indicated to improve the distinction of N1 and N2 disease.