Technical issues and pathologic implications of sentinel lymph node biopsy in early-stage breast cancer patients

Recent studies have demonstrated that the sentinel lymph node (sN) can be considered a reliable predictor of axillary lymph node status in breast cancer patients. However, some important issues, such as optimization of the technique for the intraoperative identification of the sN, and the clinical implications of sN metastasis as regards the surgical management of the axilla still require further elucidation. The objectives of this study was to assess (1) the feasibility of sN identification with a combined approach (vital blue dye lymphatic mapping and radioguided surgery, RGS) and the specific contribution of either techniques to the detection of the sN, and (2) the correlation between the size of sN metastasis (micrometastasis < or = 2 mm; macrometastasis > 2), primary tumour size, and the status of nonsentinel nodes (nsN) in the axilla.

Between October of 1997 and December of 1999, 212 patients with breast cancer (average age: 61 years; range, 40-79 years) underwent sN biopsy before performing standard axillary dissection. In a subset of 153 patients, both vital blue dye (Patent Blue-V) lymphatic mapping and RGS were used to identify the sN, and the relative contribution of each of the two techniques was assessed.

Overall, the sN was identified in 206 of 212 patients (97.1%); at histologic examination of all dissected nodes, 77 of 206 patients had positive nodes (37.3%). The false-negative rate was 6.5% (5/77), the negative predictive value was 96.3% (129/134), and accuracy was 97.6% (201/206). Among 72 patients with positive sN, micrometastases were detected in 21 cases and macrometastases in 51. When micrometastases only were observed, the sN was the exclusive site of nodal metastasis in 17 of 21 cases (80.9%); in the remaining 4 cases (19.1%), nsN metastases were detected in 3 of 14 pT1c patients (21.5%), and 1 of 5 pT2 patients (20%). Macrometastases were detected in patients with tumors classified as pT1b or larger: the sN was the exclusive site of metastasis in 3 of 4 pT1b patients (75%), in 14 of 29 pT1c patients (48.2%), and in 3 of 18 pT2 patients (16.6%). The specific contribution of the two different techniques used in the identification of the sN was evaluated; the detection rate was 73.8% (113 of 153) with Patent Blue-V alone, 94.1% (144 of 153) with RGS alone, and 98.7% (151 of 153) with Patent Blue-V combined with RGS (P < 0.001). Noteworthy, whenever the sN was identified, the prediction of axillary lymph node status was remarkably similar (93-95% sensitivity; 100% specificity; 95-97% negative predictive value, and 97-98% accuracy) with each of the three procedures (Patent Blue-V alone, RGS alone, or combined Patent Blue-V and RGS).

Sentinel lymphadenectomy can better be accomplished when both procedures (lymphatic mapping with vital blue dye and RGS) are used, due to the significantly higher sN detection rate, although the prediction of axillary lymph node status remains remarkably similar with each one of the methods assessed. That patients with small tumours (<1 cm) and sN micrometastasis are very unlikely to harbour metastasis in nsN should be considered when planning randomised clinical trials aimed at defining the effectiveness of sN guided-axillary dissection.