Dr. Hunt said earlier studies have suggested that some nodal disease is not clinically relevant and requires no treatment. However, with SLN surgery, "the more that we look, the more we find these micrometastases, and the bias is to treat them."
With improved adjuvant therapy, "we are eradicating disease with those treatments. We know that from neoadjuvant trials as well," Dr. Hunt added. In trials at MD Anderson, after chemotherapy 25% of patients who had fine-needle biopsy at initial diagnosis have complete eradication of disease in the nodes, she said.
"Now that we understand more about the subtypes, we see that in HER-2 positive disease, we’re eradicating about 75% of the disease in regional nodes with targeted therapies." Systemic therapy has gotten better, but it also appears that there are metastases that are not clinically or biologically relevant.
Because the first site of failure is generally the only site recorded, the researchers also performed a competing risk regression model to account for patients with local, regional, and distant recurrences. Evaluating competing risks demonstrated that hormone receptor–negative disease and lack of systemic chemotherapy are associated with increased risk of local recurrence. Older age, higher tumor size, greater tumor grade, and local recurrence predicted decreased survival.
Dr. Bass observed that currently, staging is based largely on the features of the primary tumor – gene assessments, tumor markers, and so on. In light of this, she wondered how long will it will be necessary to surgically stage the clinically negative axilla in patients with early-stage disease who are treated with breast-conserving therapy.
"Do the results of this trial mean that it might be possible to forgo sentinel lymph node staging of the axilla in some patients?" she asked.
That question remains to be answered, according to Dr. Hunt. Planning is underway for a trial in early-stage breast cancer to compare SLN surgery with no treatment of the axilla. "This is based on the fact that we know that different biologic subtypes have very different local and regional recurrence patterns." So, for example, in women with HER-2 positive or triple-negative disease, the systemic treatment regimen is clear with or without nodal involvement.
The researchers reported that they have no relevant conflicts of interest.
The complete manuscript of this presentation is anticipated to be published in the Annals of Surgery pending editorial review.