At the 2024 San Antonio Breast Cancer Symposium^®, experts will explore the pros and cons of omitting axillary staging for estrogen receptor-positive breast cancer during Clinical Controversies: Omission of Axillary Staging in ER-Positive Breast Cancer: Implications on Adjuvant Therapies on Thursday, December 12, from 2 to 3 p.m. CT in Stars at Night Ballroom 1-2 at the Henry B. Gonzalez Convention Center.

Presenters will highlight a new approach to de-escalation in the axilla using data that examine the outcomes of patients who did and did not undergo axillary staging. They will also discuss de-escalation of nodal irradiation, as examined in the NSABP B-51 trial, and the controversies regarding its application in practice.

For years, axillary l staging using sentinel lymph node biopsy (SLNB) was used, regardless of a patient’s specific disease characteristics, to determine if a patient had lymph node metastases, which would in turn dictate whether they received chemotherapy. As time passed, more patients with node-negative disease began to receive chemotherapy, but nodal status was still used for therapy selection in many cases, said session moderator Monica Morrow, MD.

Data from the TAILORx and RxPONDER trials, however, provided a different view of axillary staging to select systemic therapy in hormone receptor-positive, HER2-negative women. Collectively they showed that high-risk node-negative breast cancer did not benefit from chemotherapy, whereas premenopausal women with node-positive disease did benefit from the addition of chemotherapy, regardless of risk.

“Those data caused us to question why we were still doing axillary staging in clinically node-negative hormone receptor-positive/HER2-negative, postmenopausal women,” Dr. Morrow said.

Dr. Morrow, who is Chief of Breast Cancer Surgery at Memorial Sloan Kettering Cancer Center, noted that the SOUND phase III randomized clinical trial opened the door to stopping axillary staging altogether.

“Regarding the SOUND data, a lot of clinicians were giving regional node irradiation to anyone with nodal metastases, which means, when you de-escalate therapy by omitting the SLNB, you would be undertreating nine percent of women, which is the argument some make for keeping axillary staging,” Dr. Morrow explained. “In addition, clinicians don’t really know now if a patient is microscopically node negative, which raises the question of what is the least morbid thing to do: just do sentinel node biopsy and give partial breast irradiation or skip the sentinel node biopsy and give accelerated whole-breast irradiation.” 

During the 2024 SABCS^®, the Clinical Controversies session will address the ways these trials have changed practice, as well as remaining questions, such as how to accurately calculate the risk-benefit ratio of giving CDK4/6 inhibitors in the absence of nodal staging and how eliminating nodal staging might interface in the future with the results of studies in histologically node-negative women via examining the omission of breast irradiation in those with tumors determined to be low risk by molecular assays.

The session will also help attendees interpret results of the NRG Oncology/NSABP B-51/RTOG 1304 trial, presented at the 2023 SABCS^®. This trial found that it may be possible for some patients with nodal metastases at presentation who downstage with neoadjuvant chemotherapy to avoid adjuvant regional nodal irradiation without affecting risk for disease recurrence or death.

According to Dr. Morrow, how to apply these results in practice has been controversial.

“Although there were no statistically significant differences among subgroups, there was a suggestion that maybe things might be different in hormone receptor-positive versus triple-negative patients, so maybe longer follow-up was needed,” she said.

Dr. Morrow emphasized that this session will highlight the importance of multidisciplinary collaboration to provide the latest advances to patients safely.