Real-world evidence backs the cautious omission of axillary surgical staging in postmenopausal patients with hormone receptor (HR)–positive, HER2-negative breast cancer, meeting the criteria for the phase 3 SOUND trial (NCT02167490), as per findings shared at the 25th American Society of Breast Surgeons Annual Meeting.
In a real-world scenario, 87.8% of patients eligible for the SOUND trial had no positive sentinel lymph nodes (SLNs), compared to 84.6% in the trial’s SLNB arm. Additionally, axillary lymph node dissection (ALND) rates were 2.6% and 6.4%, respectively, with 0.9% and 0.6% of patients reporting four or more positive LNs.
Adjuvant systemic therapy options for the SOUND-eligible population and the SOUND trial’s SLNB cohort included hormone therapy alone (80.1% vs. 77.5%), chemotherapy only (2.9% vs. 6.9%), and combined hormone therapy with chemotherapy (6.7% vs. 13.1%). Locoregional recurrence affected 1.3% and 1.7% of patients, while distant metastasis was reported in 0.3% and 1.8%, respectively.
Among 199 postmenopausal patients in the SOUND-eligible cohort, 1% had at least 4 positive nodes, all with a recurrence score of at least 25, yet chemotherapy wasn’t recommended for any.
Lead author Andreas Giannakou, MD, emphasized the comparable oncologic outcomes to the SOUND trial, noting that nodal status didn’t significantly influence adjuvant systemic therapy considerations in postmenopausal patients with a recurrence score of 25 or less.
The SOUND trial involved 1463 cT1N0 breast cancer patients with negative axillary ultrasound (AxUS), assigned to receive SLNB or no axillary staging. The 5-year distant disease-free survival (DDFS) rates were 97.7% and 98% respectively, confirming the noninferiority of omitting axillary staging compared with SLNB. Nonetheless, nodal status remains crucial in decision-making for adjuvant systemic therapy in certain breast cancer populations.
This analysis aimed to validate SOUND trial outcomes in a real-world setting, evaluating nodal disease burden and oncologic outcomes among HR-positive, HER2-negative breast cancer patients meeting the trial’s criteria. Patients with cT1N0 HR-positive, HER2-negative disease treated between 2016 and 2023 with negative preoperative AxUS for breast conservation were eligible for the analysis.
Comparisons were made between patients with and without preoperative AxUS, as well as between the SOUND-eligible population and those in the SLNB arm of the SOUND trial. The impact of nodal status and 21-gene recurrence score on chemotherapy recommendations for postmenopausal SOUND-eligible patients was also examined.
Among 3972 patients with cT1N0M0 HR-positive, HER2-negative disease, 3428 had no AxUS, while 544 did. After excluding patients with abnormal LNs on AxUS or upfront mastectomy, 408 SOUND trial-eligible patients were identified, including 312 with SLNB.
Patients with AxUS, with or without SLNB, had a median follow-up of 23.6 and 29.9 months respectively. At 3 years, locoregional recurrence rates were 0.0% vs. 0.03%, distant recurrence rates were 1.0% vs. 0.03%, invasive disease-free survival rates were 98.0% vs. 98.5%, and overall survival rates were 98.9% vs. 98.9%, respectively.
Compared to those without AxUS, patients with AxUS were more likely to be younger and premenopausal, while those without AxUS tended to have larger tumors, higher tumor grades, and underwent mastectomy more frequently.
The median age was 57 years in the SOUND-eligible population and 60 years in the SLNB arm of the SOUND trial. Additionally, most patients in each group had ductal histology, grade 2 disease, underwent lumpectomy, and received radiotherapy.