Methylene Blue as Inexpensive and Reliable Sole Sentinel Lymph Node Mapping Agent for Patients with Invasive Ductal Carcinoma

Background: Invasive ductal cancer (IDC) represents about 75% of all breast malignancies. There are many breast cancer prognostic factors, but the ones that have the most impact on the survival rates in advanced breast cancer are tumor size and regional lymph node involvement. Axillary lymph node dissection (ALND) has particularly important and undoubtful role in current surgical options for breast cancer treatment. With the introduction of sentinel lymph node biopsy (SLNB) for breast cancer patients it was possible to identify those to whom regional spread of the disease did not occur at the time of surgery, and thus spare them an unnecessary ALND procedure. Objective: To determine the rate of sentinel lymph node (SLN) detection using only methylene blue dye as a mapping agent, as well as to correlate the number of positive SLNs with the number of positive non-sentinel lymph nodes (non-SLNs). Methods: The study represents a prospective study that included 50 female patients with histologically confirmed invasive ductal carcinoma (IDC) who underwent SLNB using only methylene blue dye as the mapping agent, while the detection and harvest of SNL was done by visual control only. All patients also underwent an obligatory complete ALND, which was as that time the institutional oncological protocol for surgical treatment of histologically confirmed IDC. The final data such as tumor size, SLN and non-SLN status were obtained by further analysis of pathohistological reports from tumor biopsy and other surgical specimens. Results: The accuracy rate of SLN detection was 98%. The number of detected SLN was in the range of 1 to 6, with an average of 2 for each patient. The number of positive SLN was in significant correlation with the number of tumor-affected non-SNL (p<0,001). Further analysis showed that for each increase in the number of positive SLN by 1, the risk of positive non-SLN increased 6-fold, OR=6,22 (p<0,001). Conclusion: Use of methylene blue dye as a sole mapping agent when performing SLNB in patients with IDC is a reliable and effective method that can be safely implemented in medical institutions that lack availability of nuclear medicine services or significant monetary funds.