P3-07-25: Sentinel Lymph Node Mapping in Breast Cancer after Primary Chemotherapy.

Abstract Background The High false negativity rate and the possible of interference of primary systemic treatment (PST) and biopsy on the lymphatic drainage in the breast and axilla are the disadvantages of sentinel lymph node biopsy (SNB) after PST. The primary aim of our study was to evaluate success rate for identification and isolation of sentinel lymph node (SLN) in patients treated with PST. Secondary aims were to verify if chemotherapy and biopsy can really alter the lymphating drainage, and to identify biological and clinical factors that can influence the accuracy of this technique. Methods: Between June 2000 and April 2007, 176 consecutive operable or locally advanced breast cancer patients (T1-4N0-1M0) treated with antracyclin-based PST were enrolled in this single Institution study. Before performing a surgical biopsy and starting the treatment a lymphatic mapping was performed and the skin projection of the SLN location was then marked with permanent ink, with the aim to verify if the SLN marked did not change after biopsy and PST. Results: The SLN was removed in 164 patients, with an identification rate of 93.2% (95% confidence interval (CI) = 89.4−96.9%). Fifty patients (30.5%) had metastatic involvement at SNB, and in 21 (42.0%) of them the SLN was the only positive node. Nine patients (5.5%) had a false negative SLN. The false-negative rate was 15.3% (95% CI = 7.1−32.9%). The SNB revealed a sensitivity of 84.7% (95% CI = 73.0−96.4%), an accuracy of 94.5% (95% CI = 90.1−99.0%) and a negative predictive value of 92.1% (95% CI = 85.8−98.4%). In 163 patients (99.4%) the SLN marked at baseline was the same removed at the end of treatment, while only in 1 case (0.6%) a different SLN was identified by the lymphatic mapping performed with radioactive colloid. According to clinical and tumor characteristics the rate of identification and removal of SNB was higher in patients aged <50 (95.6%) vs >50 (91.6%), with clinical node negative (95.1%) vs positive (88.6%) and with lower grade G2 (98.0%) vs G3 (91.2%). False negative rate of SNB was higher in patients aged >50 (17.9%) vs <50 (10.0%) and with clinical node negative (17.1%) vs positive (12.5%). Lymph node involvement was significantly associated with baseline ER positivity (p=0.00595 Chi-square test). Conclusion: The identification rate, sensitivity and accuracy do not differ from other study of SNB after PST. The false-negative rate is still high and we are performing analysis to identify biological and clinical features that can influence the accuracy of this technique. To our knowledge this is the first study with an in vivo demonstration that chemotherapy and biopsy do not alter the lymphatic drainage of the breast. We are perfoming exploratory analyses to evaluate the influence of false-negative rate of SNB on overall survival (OS) and progression free survival (PFS). Citation Information: Cancer Res 2011;71(24 Suppl):Abstract nr P3-07-25.