Gamma probe sentinel node localization and biopsy in breast cancer patients treated with a neoadjuvant chemotherapy scheme

The aim of this study was to analyse the accuracy of scintigraphic and gamma probe sentinel node (SN) localization in breast cancer patients who have been submitted to neoadjuvant chemotherapy (NC). Seventy-six patients with single breast cancer were included in the study, and were classified into two groups. Group 1 consisted of 40 women who had received NC, and Group 2 consisted of 36 women who did not receive NC. All patients received 111 MBq (3 mCi) of 99Tcm-nanocolloid in 3 ml, by peritumoural injection. Anterior and lateral thoracic scans were obtained 2 h post-injection. The following day (18-24 h post-injection) the patients underwent surgery and sentinel nodes were localized by using a gamma probe. Complete axillary lymph node dissection was performed in all patients. Histological analysis included haematoxylin-eosin in all cases and immunohistochemistry in 10 cases. In Group 1, SNs were localized in 36/40 patients, histological analysis was performed in 34 and there were four false negatives (22%). In Group 2, SNs were localized in 32/36 patients, histological analysis was performed in 29 and there were two false negatives (9%). Predictive negative values were 78% and 90% in Groups 1 and 2, respectively. In summary, sentinel node localization in breast cancer patients submitted to previous neoadjuvant chemotherapy is less accurate than in patients who do not receive this therapy. The procedure is not sufficiently accurate to localize the sentinel node, thus it cannot be recommended in these patients.