Omitting Sentinel Lymph Node Biopsy Is Safe in Select Patients With HR+ Early Breast Cancer

Omitting sentinel lymph node biopsy (SLNB) demonstrated noninferiority with regional control or survival compared with performing SLNB in patients with grade 1/2, stage cT1 to 2N0 hormone receptor (HR)–positive, HER2-negative breast cancer aged 50 years or older, according to results from the Dutch phase 3 BOOG 13-08 trial (NCT02271828), which were presented in a press briefing during the 2025 San Antonio Breast Cancer Symposium.^1,2

Data showed that, with 5 years of median follow-up, among patients who did not undergo SLNB (n = 824) and those who did (n = 748), 88 and 59 total events occurred, respectively. The local recurrence rates in each arm were 9.1% and 15.3%, and the regional recurrence rates were 9.1% and 5.1%, respectively. Contralateral breast cancer was reported in 12.5% and 22.0% of patients, and the distant metastasis rates were 29.5% and 23.7%, respectively.

Deaths on the no-SLNB arm stemmed from progressive/metastatic breast cancer (37%), second non-breast cancer (46%), other known cause (9%), and unknown cause (9%). On the SLNB arm, these rates were 30%, 35%, 20%, and 15%, respectively.

“These findings indicate that omission of the SLNB may be safely considered in case of patients over the age of 50 with HR-positive, grade 1/2, T1 breast cancer,” lead study author Marjolein Smidt, MD, PhD, said in the press briefing. “Endocrine therapy does not seem to be a prerequisite for the no-SLNB strategy in that subset. For the whole group, since we also included a significant amount of T2 tumors, we think more mature data need to be awaited.”

Smidt, a professor of surgical oncology at Maastricht University Medical Center in the Netherlands, explained that prior studies have demonstrated the safety of less axillary treatment and that systemic treatment is often biology-based. She added that in patients with early breast cancer, sentinel nodes often have negative status.

In the BOOG 13-08 trial, investigators evaluated whether omitting SLNB in patients with early breast cancer who underwent breast-conserving surgery and whole-breast radiation is safe. A total of 1733 female patients at least 18 years old with early unilateral breast cancer who underwent both surgery and radiation were enrolled; patients were across 25 centers in the Netherlands from 2015 to 2022.

Of the 1574 evaluable patients, following surgery and radiation, patients either underwent SLNB (arm A; n = 748) or no SLNB (arm B; n = 824). In arm A, if they were indicated, they were given axillary treatment. In both arms, if indicated, patients were then moved onto systemic therapy.

The median age of patients was 61.9 years, with most patients being 50 years or older. Additionally, most patients had stage T1 disease (83%), grade 1/2 disease (82%), and were mostly HR-positive, HER2-negative. Eighty-six percent of patients had negative SLN, and 14% had metastatic disease; 17% received chemotherapy with or without targeted therapy, and 44% received endocrine therapy.

Additional results showed that the median 5-year regional recurrence-free survival rate was 96.6% in those who underwent SLNB compared with 94.2% in those who did not, leading to an absolute difference of 2.35%. The median 5-year distant disease-free survival rate was 96.0% vs 92.9%, respectively, with an absolute difference of 3.3%.

“The upper border of the confidence interval was 4.72, which means noninferiority is not exceeded,” Smidt said.

Prior results from the SOUND (NCT02167490)³ and INSEMA (NCT02466737)⁴ trials showed consistent findings with the BOOG 13-08 trial in this patient population. In SOUND and INSEMA, enrolled patients had HR-positive, HER2-negative disease that was cT1; patients were older than 50 years. Sixty percent of patients from these 2 studies (n = 949) were from the BOOG 13-08 trial (S/I selection), Smidt explained.

In the S/I selection cohort of BOOG 13-08 (n = 508), in which patients did not have SLNB, the local recurrence, regional recurrence, contralateral breast cancer, and distant metastasis rates were 1.4%, 0.6%, 1.8%, and 2.2%, respectively. In SOUND, of patients with no SLNB (n = 697), these rates were 0.9%, 0.7%, 1.0%, and 2.0%, respectively. In the INSEMA cohort of patients with no SLNB (n = 962), these rates were 0.8%, 1.0%, 1.0%, and 2.7%, respectively.

Deaths due to progressive/metastatic disease, second non-breast cancer, other known cause, and unknown cause occurred in 0.6%, 1.6%, 0.2%, and 0.4% of those in the S/I selection on BOOG 13-08. A total of 0.6% died from progressive/metastatic disease on SOUND, and 1.7% and 0.3% died from other known causes and unknown causes, respectively. On INSEMA, 0.7% and 0.6% of patients died from other known cause and unknown cause, respectively.

Smidt explained that when the SOUND/INSEMA findings were applied, it demonstrated that BOOG 13-08 had comparable outcomes.

Disclosures: Smidt cited being an employee of MUMC+; grant/research support from KWF, NOW, Illumina, Servier Pharma, TKI, Nutricia, Roche; and additional financial relationships to disclose as part of the BOOG 13-08 trial from Dutch Cancer Society, CZ, and the Netherlands Organization for Health Research and Development.

References

1. Smidt ML, Schipper RJ, van Roozendaal VM, et al. Omission of sentinel lymph node biopsy in clinically T1-2 node-negative breast cancer patients treated with breast-conserving therapy: results of the Dutch BOOG 2013-08 randomized controlled trial after a median follow-up of 5 years. Presented at: 2025 San Antonio Breast Cancer Symposium; December 9-12, 2025; San Antonio, TX. Abstract GS2-11.
2. Sentinel lymph node biopsy may be safely omitted in some patients with early-stage breast cancer. American Association of Cancer Research. News release. Published December 11, 2025. Accessed December 11, 2025. https://tinyurl.com/3ebskbt7
3. Gentilini OD, Botteri E, Sangalli C, et al. Sentinel lymph node biopsy vs no axillary surgery in patients with small breast cancer and negative results on ultrasonography of axillary lymph nodes: the SOUND randomized clinical trial. JAMA Oncol. 2923;9(11):1557-1564. doi:10.1001/jamaoncol.2023.3759
4. Reimer T, Stachs A, Veselinovic K, et al. Axillary surgery in breast cancer — primary results of the INSEMA trial. N Eng J Med. 2925;392(11):1051-1064. doi:10.1056/NEJMoa2412063