5-year data back omission of sentinel lymph node biopsy in early-stage breast cancer

Sentinel lymph node biopsy (SLNB) may be safely omitted after breast-conserving therapy in patients with early-stage, node-negative breast cancer, with 5-year data from the BOOG 13-08 trial showing no difference in regional recurrence-free and distant disease-free survival outcomes whether or not SLNB was performed.

In the per-protocol analysis, the primary endpoint of 5-year regional recurrence-free survival was 96.6 percent (95 percent confidence interval [CI], 95.2–98) in the SLNB arm vs 94.2 percent (95 percent CI, 92.4–96) in the no-SLNB arm (absolute difference, 2.35 percent, 95 percent CI, 0.06–4.72). [SABCS 2025, abstract GS2-11]

Distant disease-free survival at 5 years was 96 percent (95 percent CI, 94.4–97.6) in the SLNB arm vs 92.9 percent (95 percent CI, 90.9–94.9) in the no-SLNB arm (absolute difference, 3.3 percent).

The difference observed in both outcomes met the prespecified noninferiority criteria for omitting vs performing SLNB, reported first study author Dr Marjolein Smidt from Maastricht University Medical Center in Maastricht, Netherlands.

BOOG 13-08 trial

For the BOOG 13-08 trial, Smidt and colleagues enrolled women with unilateral cT1-2N0 breast cancer treated with breast-conserving surgery and whole-breast irradiation. These women were randomly assigned to either undergo SLNB or not.

The intention-to-treat analysis included 1,701 patients, while the per-protocol analysis included 1,572 (824 in the no-SLNB arm, 748 in the SLNB arm). In both study arms, the mean patient age was 61 years, and more than 80 percent had cT1 and grade 1/2 disease and were HR-positive/HER2-negative. Among HR-positive patients, more than 40 percent of patients received endocrine therapy, and around half received no systemic therapy at all.

A total of 88 primary and secondary endpoint events occurred in the no-SLNB arm. These comprised eight local recurrences, eight regional recurrences, 11 contralateral breast cancers, 26 distant metastases, and 35 deaths. In the SLNB arm, there were 59 primary and secondary endpoint events: nine local recurrences, three regional recurrences, 13 contralateral breast cancers, 14 distant metastases, and 20 deaths.

Of the deaths, 13 in the no-SLNB arm and six in the SLNB arm were attributed to metastatic breast cancer, while 16 and seven, respectively, were due to second non-breast cancers.

According to Smidt, the number of primary and secondary endpoint events in the no-SLNB arm is in line with those reported in the no-SLNB populations in SOUND and INSEMA trials, which similarly involved patients with clinical T1 breast cancer treated with breast-conserving therapy.

Takeaway

Overall, the findings indicate that “SNLB omission may be safely considered” in breast cancer patients more than 50 years of age and have HR-positive/HER2-negative, grade 1-2, T1 disease, Smidt said. “Endocrine therapy does not seem to be a prerequisite for SLNB omission in this subset.”

However, for the entire BOOG 13-08 population, more mature data are needed, she added.