De-escalation of Axillary Surgery in Early Breast Cancer: Translating SOUND and INSEMA into Clinical Practice.

OBJECTIVE

To prospectively evaluate how often axillary staging can successfully be omitted in postmenopausal HR+/HER2- patients.

BACKGROUND

Three randomized trials showed no difference in recurrence or survival outcomes with omission of sentinel lymph node biopsy (SLNB) in cT1-T2N0 patients with a negative axillary ultrasound (AUS) undergoing breast-conserving surgery (BCS). We prospectively evaluated applicability of this approach.

METHODS

From 3/1/24 to 9/1/25, SLNB was omitted in postmenopausal women age 50-70 years with unicentric or multifocal, clinical stage 1, grade 1/2, HR+/HER2- cancers and a normal AUS undergoing BCS. After the results of INSEMA were reported, tumors up to 2.5 cm were included. Patients with pathology showing grade 3, T≥3 cm, or HR- or HER2+ underwent multidisciplinary discussion regarding the need for SLNB.

RESULTS

In 437 patients with 442 cancers, the median patient age was 63 years, median mammographic tumor size was 0.9 cm, and 74% were grade 2. A total of 34 patients (8%) had high-risk features on final pathology (grade 3, n=20; T≥3 cm, n=11; HER2+, n=3) and 14 (3.2%) had SLNB. Of these, 2 had SLN metastases. A total of 96% of patients received radiotherapy (40% whole breast, 56% partial breast), 415 (95%) received adjuvant endocrine therapy, and 31 (7%) received chemotherapy. At 7.7-month median follow-up, there have been no axillary recurrences.

CONCLUSION

Adoption of the SOUND, INSEMA, and BOOG 13-08 data allowed omission of SLNB in 97% of postmenopausal patients age ≤70 years with cT1-2N0, grade 1/2, HR+/HER2- cancers and a normal AUS, reducing the burden of treatment.