Foregoing sentinel lymph node (SLN) surgery does not increase rates of radiation therapy treatment or whole-breast irradiation (WBI), according to results presented May 1 at the American Society of Breast Surgeons (ASBrS) annual meeting in Seattle.
Presenter Matthew Hager, MD, from the Mayo Clinic in Rochester, MN, showed how women undergoing lumpectomy who omit SLN surgery are no more likely to undergo escalation of radiation therapy than women with similar tumors who underwent SLN surgery.
“Today a growing number of well-selected patients with low-risk breast cancer are being spared SLN surgeries,” Hager said. “Our study is one of the first to examine radiation therapy in the setting of nodal surgery omission.”
Recent trials suggest that omitting SLN surgery is an option for select women who are undergoing breast conservation therapy. These include the Sentinel Node Versus Observation After Axillary UltraSouND (SOUND) trial and Intergroup Sentinel Mamma (INSEMA) trial.
Because of these results, some practices are omitting SLN surgery for women over age 50 who have early-stage clinically node-negative, hormone receptor-positive, HER2-negative breast cancer.
Hager and colleagues studied trends in use of SLN surgery and radiation therapy and how foregoing SLN surgery impacts radiation therapy. They focused on two areas: whether omitting SLN is tied to greater use of WBI and lower use of partial breast irradiation in women ages 50 to 69 years, and whether omitting it affects radiation therapy omission in women 70 years or older.
The study included 1,016 breast cancers among 999 women who underwent breast conservation surgery. About one-third of the women did not undergo SLN surgery while about two-thirds did.
Hager reported that SLN surgery significantly decreased from 74.5% in 2020 to 49.1% in 2025 (p < 0.001). Women who underwent SLN surgery compared to those who did not shared the following factors: they were younger (age 64 versus 76, p < 0.001); stage 2 cancer was more common (19.2% versus 6.5% p < 0.001); cancer grade was higher (59.9% versus 48.5%, p = 0.001); and they were more likely to undergo radiation therapy (92.5% versus 72.5%, p < 0.001).
Among those who did not undergo SLN surgery, partial breast irradiation was the most common treatment at 51%. Radiation therapy was next, at 27.5% and WBI was performed in 21.5%. Rates of partial breast irradiation among this group increased from 39.5% in 2020 to 61.1% in 2025 (p = 0.10) while WBI use increased slightly (15.8% to 24.1%, p = 0.17).
Women who did not undergo SLN surgery experienced lower rates of WBI, higher rates of partial breast irradiation, and higher rates of radiation therapy omission compared to the SLN surgery group.
Comparison in therapy rates between women who undergo or do not undergo SLN surgery | |||
Measure | SLN surgery group | SLN surgery omission group | P-value |
WBI rate | 50.9% | 21.5% | <0.001 |
Partial irradiation rate | 41.6% | 51% | 0.004 |
Radiation therapy omission | 7.5% | 27.5% | <0.001 |
Women in the omission group who underwent radiation therapy were more likely to undergo partial breast irradiation (75%) compared to WBI (25%). Hager reported the opposite trend for women who had SLN surgery (52.7% for WBI versus 47.3% partial irradiation).
Finally, 11.1% of women between the ages of 50 and 69 years who forewent SLN surgery also did not have radiation therapy, compared to 5.8% of the SLN surgery group (p = 0.19). And women aged 70 and older who forewent SLN surgery were more likely to have partial breast irradiation (48.6%) or omission (30%) of radiation therapy compared to WBI (21.4%). Hager added that the opposite trend went for women who underwent SLN surgery.
Patients benefit from avoiding potentially risky treatment for breast conservation, according to Hager.
“This suggests that our multidisciplinary care team is working together in implementing advances in management and integrating information from their individual medical specialties to optimize and personalize patient care,” he concluded.
