When the analysis looked specifically at patients who were clinically node negative at presentation and had a pCR, the rates of positive lymph nodes at the time of surgery were 1.6% in HER2+ patients and 1.7% in TNBC disease, Dr. Barron said. “If there was residual disease in the breast, the nodal positivity rate was significantly higher, at 18% in HER2+ and 12% in TNBC,” she added. In those who were clinical N1, the breast pCR rates were similar – 41% in HER2+ and 35% in TNBC – but nodal positivity rates were significantly higher, at 13% and 14%, respectively.
The HR+/HER2- group had significantly lower rates of pCR: 12% in the cN0 and 13% in the cN1 subgroups. This subgroup also had higher nodal positivity rates – in the cN0 subgroup, 4% in those with a breast pCR and 34% in those with residual disease in the breast, and in the cN1 subgroup, 30% and 83%, respectively.
When the investigators looked at the extent of nodal burden in cN0 patients with breast pCR, they found the rate of N2 and N3 disease was near zero across all biologic subtypes. “In patients who were cN1 at presentation and achieved a breast pCR but had residual axillary disease, the majority had N1 disease with only 1.5%-4% having four or more positive lymph nodes,” Dr. Barron said.
In the discussion, session moderator Carla Fisher, MD, of Indiana University, Indianapolis, said, “While we might not be ready for prime time to not evaluate the lymph nodes of these patients, this study does speak to the importance of establishing N0 and N1 prior to NAC.” In reply to her question about how Mayo routinely evaluates node status prior to NAC, Dr. Barron noted that Mayo performs routine axillary ultrasound. However, the NCDB data does not specify what imaging was done. This is thought to vary across the centers in the NCDB, Dr. Barron said.
Noted Dr. Boughey, “The findings from this study provide data that can be used moving forward for planning future clinical trials.” She also said that these findings do not alter the current standard of care; that still calls for breast and nodal surgery after NAC. However, the ongoing NRG-BR005 phase II clinical trial is assessing the accuracy of tumor-bed biopsy in these situations (ClinicalTrials.gov Identifier:). “The results from that trial will help inform future trials evaluating eliminating breast surgery in patients with an excellent response to NAC,” Dr. Boughey said. “Those patients could also potentially avoid axillary surgery based on the data we have now.”
Dr. Barron and Dr. Boughey and coauthors reported having no financial disclosures.
SOURCE: Barron AU et al. Society of Surgical Oncology Annual Cancer Symposium, .