Can preoperative dynamic contrast-enhanced breast MRI predict extensive occult axillary lymph node metastases in patients with positive sentinel node biopsy?

Abstract

1049 Background: The Katz nomogram is an established clinical-pathologic tool to identify patients with a high likelihood of harboring ≥ 4 occult axillary lymph nodes after a positive sentinel lymph node biopsy. This study examines the ability of preoperative Dynamic Contrast Enhanced MRI (DCE-MRI) to predict which sentinel node positive patients will ultimately have ≥ 4 total positive axillary lymph nodes upon completion axillary dissection and assesses whether DCE-MRI can add predictive value to the Katz nomogram. Methods: Retrospective review of consecutive patients (6/2005 – 12/2009) undergoing sentinel lymph node biopsy was conducted to identify those with invasive breast cancer, clinically negative axillae, preoperative DCE-MRI and positive sentinel node biopsy. Patients who received preoperative chemotherapy or did not undergo axillary dissection were excluded. Clinical and pathologic factors, primary lesion size, and quantitative primary lesion DCE-MRI kinetics, including initial peak enhancement, percent rapid enhancement, and percent washout were collected from clinical records and prospective databases. DCE-MRI parameters with univariate significance (p < 0.05) to predict ≥ 4 axillary nodes were modeled with stepwise regression. Results: 98 patients with 99 positive sentinel lymph node biopsies (one synchronous bilateral case) met study criteria. Stepwise regression identified DCE-MRI volume adjusted peak enhancement and total washout as significant independent predictors of ≥4 metastatic axillary lymph nodes. ROC curves demonstrated an AUC of 0.78 for the Katz nomogram, 0.78 for the DCE-MRI multivariate model, and 0.85 for a combination of the Katz nomogram and DCE-MRI. The combined model was significantly more predictive than the Katz nomogram alone (p = 0.007). Conclusions: DCE-MRI primary lesion kinetics significantly improved the accuracy of the Katz clinical-pathologic nomogram to predict the presence of ≥ 4 axillary node metastases. With validation of these results, DCE-MRI may help predict which sentinel lymph node positive patients have more extensive occult regional adenopathy requiring further therapy.