Axillary staging in breast cancer patients treated with neoadjuvant chemotherapy in two Dutch phase III studies

Background: Primary aim of our study was to assess the impact of timing of sentinel node procedure, pre-versus post-neoadjuvant chemotherapy, on final pathologic node-negative rate (pN0) in patients with clinically node-negative (cN0) breast cancer. Secondary endpoint was the usability of the sentinel node procedure in patients with clinically node-positive disease that converted to cN0 after neoadjuvant chemotherapy.Patients and Methods: Patients were enrolled in two sequentially conducted Dutch phase III trials, studying the impact of two neoadjuvant chemotherapy schedules and use of zoledronic acid on complete pathologic response rate. For the present analyses, patients were excluded if they had not undergone surgical axillary staging.Results: In total 439 patients were included, of whom 230 (52%) had pretreatment cN0. In this group, pN0 status was seen in 58% (N = 23) of patients with a sentinel node biopsy post-neoadjuvant chemotherapy compared to 51% (N = 83) pre-neoadjuvant chemotherapy, including the axillary lymph node dissection whenever performed. In multivariable analysis, timing of sentinel node procedure (pre-versus post-neoadjuvant chemotherapy) was, however, not significantly associated with final pN0/pN0(i+) status, with an odds ratio of 1.18 (95% CI 0.64-2.18) after correction for age, clinical tumor status, histology, grade, hormone-and HER2 receptor. Of patients with clinically node-positive disease only 15% had a final pN0 status, with a false-negative rate of the sentinel node of 30%.Conclusion: In breast cancer patients with cN0 disease, sentinel node procedure performed post-neoadjuvant chemotherapy led to nodal down staging, although not statistically significant after multivariate correction for patient and tumor characteristics.