[Comparative study of the different radiotracer administration route to locate the sentinel node in breast cancer]

To assess the results of Sentinel Lymph Node (SLN) detection in breast cancer patients depending on the radiotracer injection route, especially evaluating which route that makes it possible to identify the highest percentage of SLNs and its detection in the inner mammary chain.

We prospectively studied 120 breast cancer patients. Three groups of 40 patients each were established depending on the radiotracer injection route. 1) Subdermal or subareolar route: 18 T1 and 22 T2, mean tumor diameter size of 1.76 cm. 2) Peritumoral route: 16 T1 and 24 T2, mean tumor diameter size of 1.86 cm. 3) Intratumoral route: 20 T1 and 20 T2, mean tumor diameter size of 1.61 cm. The day before surgery, a lymphoscintigraphic study was performed in all cases and intraoperative SLN resection was carried out with the aid of a hand-held gamma probe.

The SLN was identified in 38/40 cases (95%) of group 1, in 35/40 cases (88%) of group 2 and in 38/40 cases (95%) of group 3. No SLNs in the mammary chain were observed in patients who underwent subdermal/subareolar injection of the radiotracer. On the other hand, SLNs were visualized in this location in 4/35 patients with peritumoral injection (11%) and in 8/38 patients with intratumoral injection (21%).

The superficial (subdermal, subareolar) injection technique is more suitable when an unnecessary lymphadenectomy has to be prevented in cases without axillary metastases. The deeper injection technique (peritumoral, intratumoral) should be use when, moreover, we seek accurate staging or plan non-systematic mammary chain irradiation.