Tumor Contact With Internal Mammary Perforator Vessels as Risk Factor for Gross Internal Mammary Lymph Node Involvement in Patients With Breast Cancer

Abstract

ImportanceThe identification of internal mammary lymph node metastases and the assessment of associated risk factors are crucial for adjuvant regional lymph node irradiation in breast cancer patients. The current study aims to investigate if tumor contact with internal mammary perforator vessels is associated with gross internal mammary lymph node involvement. MethodsWe included 297 patients with primary breast cancer and gross internal mammary (IMN+) and/or axillary metastases (AXN+) as well as 230 patients without lymph node metastasis. Based on pre-treatment dynamic contrast-enhanced magnetic resonance imaging (DE-MRI), we assessed contact of the tumor to the internal mammary perforating vessels (IMPV). Results59 patients had ipsilateral IMN+ (iIMN+), 10 patients contralateral IMN+ (cIMN+) and 228 patients had ipsilateral axillary metastases without IMN. 230 patients had node negative breast cancer. In patients with ipsilateral IMN+, 100% of tumors had contact with ipsilateral IMPV with 94.9% (n=56) classified as major contact. In iIMN- patients on the other hand, major IMPV contact was observed in only 25.3% (n=116) and 36.2% (n=166) had no IMPV contact at all. Receiver operating characteristic (ROC) analysis revealed that “major IMPV contact” was more accurate in predicting ipsilateral IMN+ (AUC 0.85) compared to a multivariate model combining grade of differentiation, tumor site, size and molecular subtype (AUC 0.65). Strikingly, among patients with contralateral IMN+ (cIMN+), 100% of tumors had contact to a crossing contralateral IMPV, whereas in contralateral IMN- (cIMN-) patients, IMPVs to the contralateral side were observed in only 53.4% (iIMN+) and 24.8% (iIMN-), respectively. ConclusionTumor contact with the IMPV is highly associated with risk of gross IMN involvement. Further studies are warranted to investigate whether this identified risk factor is also associated with microscopic IMN involvement and whether it can assist in the selection of breast cancer patients for IMNI.