Breast Cancer Larger Than 2.5 Cm with Tumor-Free Radioisotope-Hot Sentinel Nodes Has Higher Risk of Non-Hot Axillary Lymph Node Metastasis

Background: Sentinel lymph node biopsy (SLNB) is the standard axillary staging approach for early breast cancer with clinically negative axillary involvement. Adequate SLNB should include the removal of not only radioactive tracer-labeled lymph nodes (hot nodes or SLNs) but also suspicious unlabeled nodes (non-hot nodes or non-SLNs). However, the biopsy of non-hot nodes is highly dependent on the surgeons' experiences. This article aims to facilitate the surgeon's decision making by elucidating parameters that correlate with non-hot node metastasis. Methods: From 2013 to 2016, clinically node-negative (cNO) breast cancer patients receiving axillary SLNB using single Tc-99m tracer method at our institute were recruited. Patients were excluded if they had received prior neoadjuvant chemotherapy. Among them, cases that have at least one non-isotope-hot node biopsied were retrospectively reviewed with a particular focus on patients with pathologically negative isotope-hot SLNs. The correlation of clinicopathological data with metastasis to axillary lymph nodes and sentinel lymph nodes was analyzed with the Chi-squared test, Fisher's exact test, and multivariate logistic regression. Receiver operating curve (ROC) was applied for continuous variables that predicted non-hot node metastasis; relapse-free survival (RFS) and locoregional relapse-free survival (LRRFS) were compared by Kaplan-Meier analysis. Results: In 632 isotope-hot SLN negative patients, T stage showed a correlation with nonisotope-hot SLN metastasis (p = 0.035, odds ratio (OR) 9.65). Tumors larger than 2.5 cm best predict non-isotope-hot SLN metastasis (area under curve (AUC) = 0.71). With a median follow up of 41.80 months, locoregional relapse-free survival was significantly worse in cases with non-hot node metastasis (66.2% vs. 69.0%, p = 0.001). Conclusion: In the setting of SLNB using single radioisotope tracer, non-hot node metastasis in cases with negative hot SLN still carries a higher locoregional recurrence rate (13.3%). For early breast cancer larger than 2.5 cm, removal of suspicious non-hot nodes should be included for a precision therapy.