Accuracy of breast MRI in evaluating nodal status after neoadjuvant therapy in invasive lobular carcinoma

Ruby Guo,Nola Hylton,Heather Greenwood,Tatiana Kelil,Judy C. Boughey,Laura J. Esserman,Rita A. Mukhtar,Cheryl Ewing,Mary Kathryn Abel,Jasmine Wong,Michael Alvarado,Case Brabham

doi:10.1038/s41523-021-00233-9

Abstract

Neoadjuvant therapy in breast cancer can downstage axillary lymph nodes and reduce extent of axillary surgery. As such, accurate determination of nodal status after neoadjuvant therapy and before surgery impacts surgical management. There are scarce data on the diagnostic accuracy of breast magnetic resonance imaging (MRI) for nodal evaluation after neoadjuvant therapy in patients with invasive lobular carcinoma (ILC), a diffusely growing tumor type. We retrospectively analyzed patients with stage 1–3 ILC who underwent pre-operative breast MRI after either neoadjuvant chemotherapy or endocrine therapy at our institution between 2006 and 2019. Two breast radiologists reviewed MRIs and evaluated axillary nodes for suspicious features. All patients underwent either sentinel node biopsy or axillary dissection. We evaluated sensitivity, specificity, negative and positive predictive values, and overall accuracy of the post-treatment breast MRI in predicting pathologic nodal status. Of 79 patients, 58.2% received neoadjuvant chemotherapy and 41.8% neoadjuvant endocrine therapy. The sensitivity and negative predictive value of MRI were significantly higher in the neoadjuvant endocrine therapy cohort than in the neoadjuvant chemotherapy cohort (66.7 vs. 37.9%, p = 0.012 and 70.6 vs. 40%, p = 0.007, respectively), while overall accuracy was similar. Upstaging from clinically node negative to pathologically node positive occurred in 28.0 and 41.7%, respectively. In clinically node positive patients, those with an abnormal post-treatment MRI had a significantly higher proportion of patients with ≥4 positive nodes on pathology compared to those with a normal MRI (61.1 versus 16.7%, p = 0.034). Overall, accuracy of breast MRI for predicting nodal status after neoadjuvant therapy in ILC was low in both chemotherapy and endocrine therapy cohorts. However, post-treatment breast MRI may help identify patients with a high burden of nodal disease (≥4 positive nodes), which could impact pre-operative systemic therapy decisions. Further studies are needed to assess other imaging modalities to evaluate for nodal disease following neoadjuvant therapy and to improve clinical staging in patients with ILC.

Highlights

One advantage of neoadjuvant therapy in the treatment of breast cancer is the potential to downstage the axilla and reduce the extent of morbid axillary surgery[1,2,3,4,5,6]
We evaluated a cohort of invasive lobular carcinoma (ILC) patients treated with either neoadjuvant chemotherapy or endocrine therapy and determined the accuracy of post-treatment magnetic resonance imaging (MRI) for predicting pathologic nodal status in both clinically node negative and clinically node positive patients
In the endocrine therapy cohort, no patients were downgraded to pathologically negative nodes at the time of surgery. In this unique cohort of patients with ILC, we evaluated the performance of breast MRI in predicting the status of axillary nodes in the setting of either neoadjuvant chemotherapy or neoadjuvant endocrine therapy and found that the overall accuracy ranged from 45.5–66.7%

Summary

Introduction

One advantage of neoadjuvant therapy in the treatment of breast cancer is the potential to downstage the axilla and reduce the extent of morbid axillary surgery[1,2,3,4,5,6]. As such, developing ways to accurately evaluate the axilla with imaging is important in the management of breast cancer patients. Given its prevalence in evaluating the in-breast response to neoadjuvant therapy, there is increasing interest in the ability of breast magnetic resonance imaging (MRI) to determine axillary status as well. Studies have evaluated the diagnostic accuracy of breast MRI for predicting axillary lymph node status after neoadjuvant chemotherapy, with accuracy ranging from 60 to 87%8–13. There are currently limited data on the accuracy of breast MRI for predicting nodal status after neoadjuvant endocrine therapy, and no data evaluating accuracy for patients with invasive lobular carcinoma (ILC) of the breast. Patients with ILC and a positive sentinel lymph node have a higher burden of additional nodal disease than the more common invasive ductal carcinoma (IDC)[15]. Standard breast imaging tools like mammography are known to have a lower sensitivity for ILC than IDC16–18

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Conclusion