Similar recurrence and regional recurrence-free survival rates were observed at 5 years with or without a sentinel lymph node biopsy in patients with clinically node-negative cT1-2 breast cancer treated with breast-conserving therapy, according to findings from the phase III BOOG 2013-08 trial presented at the 2025 San Antonio Breast Cancer Symposium (SABCS; Abstract GS2-11).
“Examination of the sentinel lymph node biopsy in cT1-2 patients with systemic therapy use [showed] comparable [recurrence rates] between treatment arms, [including] a noninferior 5-year regional recurrence-free survival. These findings indicate that omission of the sentinel lymph node biopsy may safely be considered in the case of patients over the age of 50 with T1 grade 1-2 hormone receptor–positive breast cancer,” said presenting author Marjolein Smidt, MD, PhD, Professor at the Maastricht University Medical Center in the Netherlands. “Endocrine therapy does not seem to be a prerequisite for the no-sentinel lymph node biopsy strategy in this subset.”
Background and Study Methods
Researchers have hypothesized that sentinel lymph node biopsy is beneficial prognostically but may not benefit survival outcomes or reduce the risk of recurrence in patients with breast cancer. The multicenter, randomized, noninferiority phase III BOOG 2013-08 study was created to assess if the omission of sentinel lymph node biopsy is safe in patients with clinically T1-2 node-negative breast cancer who were treated with breast-conserving surgery and whole-breast irradiation.
The trial enrolled 1,733 women across 25 centers in the Netherlands who had unilateral cT1 to T2, node-negative invasive breast cancer and who were treated with breast-conserving surgery and whole-breast radiation therapy. Participants were randomly assigned 1:1 to either receive or not receive sentinel lymph node biopsy. Stratification factors included clinical tumor size (<3 cm vs ≥3 cm), histological grade (I-II vs III), hormone receptor status, HER2 status, age (≤50, 50 ≤ 75, >75 years), primary systemic therapy, and participating center. Patients in the sentinel lymph node biopsy arm were allowed to undergo additional axillary treatment if indicated. The per-protocol analysis included 1,574 patients due to radiation therapy protocol violations.
The primary endpoint was the 5-year recurrence rate; noninferiority was considered achieved if there was an absolute difference in recurrence rate of 5% or less at 5 years in favor of the control group.
Key Findings
The median follow-up was 5 years. At 5 years, the recurrence rate in the sentinel lymph node biopsy arm was 0.5% (95% confidence interval [CI] = 0.0–1.1) as compared with 1.2% (95% CI = 0.4–2.0) in the no–sentinel lymph node biopsy arm. The absolute difference was 0.7% (95% CI = –0.3 to 1.7).
Regional recurrence–free survival rates at 5 years were 96.6% (95% CI = 95.2%–98.0%) with sentinel lymph node biopsy and 94.2% (95% CI = 92.4%–96.0%) without (log-rank P = .063). There were eight local recurrence events in the biopsy arm and nine in the no-biopsy arm.
Distant disease–free survival rates were 96% for the sentinel lymph node biopsy arm and 92.9% for the no-biopsy arm at 5 years. Distant metastatic disease was reported in 26 patients who did not receive a sentinel lymph node biopsy vs in 14 who did. Thirty-five patients from the no sentinel lymph node biopsy arm died (13 related to breast cancer) vs 20 in the biopsy arm (6 related to breast cancer).
Primary systemic therapy consisted of chemotherapy or endocrine therapy in 11.3% of patients (12.3% in the biopsy arm and 10.3% in the no-biopsy arm; P = .214). Half of all patients received some systemic therapy (51.2% in the biopsy arm vs 49% in the no-biopsy arm; P = .202), including 39.4% who received chemotherapy with or without targeted therapy.
Specifically in patients with ER-positive breast cancer, 48.6% in the biopsy arm and 46.6% in the no-biopsy arm received adjuvant endocrine therapy (P = .732), and 9.8% and 8.2%, respectively, received chemotherapy (P = .532).
Further Context
Two studies have previously explored the possibility of omitting sentinel lymph node biopsy in patients with breast cancer, and demonstrated that it could safely be omitted in patients with grade I-II cT1 hormone receptor–positive/HER2-negative breast cancer over the age of 50. Dr. Smidt noted that were comparable outcomes in the BOOG 2013-08 trial.
Disclosure: The study was funded by the Dutch Cancer Society, Central Health Insurance, and the Netherlands Organization for Health Research and Development. Dr. Smidt reported receiving funding from Roche, Nutricia, and Servier Pharma, and material from Illumina. For full disclosures of the study authors, visit abstractsonline.com.
