Intraoperative imprint cytology examination of sentinel lymph nodes after neoadjuvant chemotherapy in breast cancer patients.

Background: Intraoperative imprint cytology (IC) is one of several accurate, proven methods to detect tumor cells in sentinel lymph nodes (SLN) from patients with operable breast cancer. In patients treated with neoadjuvant chemotherapy (NAC), studies have demonstrated the feasibility and accuracy of SLN biopsy procedure. We evaluated the validity of IC for SLN testing in patients after NAC.
Material and Methods: Patients with infiltrating breast carcinoma receiving NAC (n = 132) were studied prospectively. At surgery, SLN biopsy followed by axillary lymph node dissection was performed. SLN were evaluated using IC in 80 of 132 patients (60%). The results of IC in the adjuvant setting (100 patients) were used for comparison.
Results: SLN metastases were correctly identified using IC in 58 of 80 (72%) patients. False negative results were observed in 21 patients. The sensitivity of IC testing was 38.2% and specificity 97.8%. The positive and negative predictive values (PPV and NPV) were 92.9% and 68.2%, respectively. In univariate analysis and multivariate logistic regression analysis, patients with micrometastases or isolated tumor cells in SLN have 2.3 times higher risk of a false negative IC result than patients with macrometastases in SLN (P = .00021; relative risk [RR] = 2.3; 95% confidence interval, 1.37-3.85). The non-NAC group, which contained fewer micrometastatic cases, showed better sensitivity (47.4%) and NPV (88.9%).
Conclusion: NAC does not seem to influence the accuracy and sensitivity of IC. Variations in sensitivity are related to the proportion of cases with micrometastases and ITC, as it was also shown in chemonaive patients.