SLN Surgery Omission Does Not Increase Radiotherapy Use in Breast Cancer

Patients 50 and older with breast cancer who had omission of sentinel lymph node (SLN) surgery were not more inclined to escalate to radiation therapy compared with patients with similar tumors who received SLN surgery, according to a presentation from the 2026 American Society of Breast Surgeons Annual Meeting.

For 617 patients who received SLN surgery at pN0, 46.4% had whole breast irradiation (WBI), 45.6% had partial breast irradiation (PBI), and 8.0% had no radiation. For those who did not receive SLN surgery, WBI occurred in 21.5%, 51.0% had PBI, and 27.5% had no radiation.

When looking at patient age, among those 70 and older, SLN omission was noted in 69.1% of patients. Furthermore, for those who had SLN surgery, WBI occurred in 56.3%, PBI in 28.9%, and no radiation in 14.8% compared with WBI in 21.4%, PBI in 48.6%, and no radiation in 30.0% among patients without SLN surgery.

For those 50 years and younger who received SLN, WBI occurred in 49.6%, PBI in 44.5%, and no radiation in 5.8% compared with WBI in 22.2%, PBI in 66.7%, and no radiation in 11.1% among those who did not receive SLN.

“Omission of SLN surgery significantly increased from 2020 to 2025, initially in those 70 or older, and more recently in patients aged 50 to 69,” Matthew Hager, MD, a fellow in the Department of Breast and Melanoma Surgical Oncology at the Mayo Clinic in Rochester, MN, said during the press briefing of the study.

From January 2020 to August 2025, patients treated at Mayo Clinic Rochester who were female and aged 50 or older; had cT1/cT2, cN0, M0, estrogen receptor–positive/HER2-negative breast cancer; and were treated upfront with breast-conserving surgery were included in this study. Investigators looked at the type of axillary surgery plus the type of radiation.

Investigators performed statistical analysis via Cochran-Armitage trend tests based on SAS. P values of less than 0.05 were considered to be statistically significant.

For those who did not receive SLN (n = 337), the median age was 76 years vs 64 years in the SLN group (n = 679; P <.0001). Clinical T category of cT1 was noted in 93.5% of patients vs 80.9% (P <.0001), cN0a in 87.2% vs 83.4% (P = .11), and grade 1 disease in 51.5% vs 40.1% (P <.0001). Additionally, the median Ki67 value was 8.0 vs 10.0, respectively (P = .001).

Looking at pathologic characteristics, most patients had pT1 disease in 89.9% vs 80.3% of patients without and with SLN surgery, respectively, followed by pT2 disease in 9.5% vs 18.6%. Of note, 3 of 62 patients with pN1 disease underwent axillary lymph node dissection. Looking at pathologic N category, 0.3% vs 90.9% of patients had pN0, 0.0% vs 9.1% had pN1, and 99.7% vs 0.0% had pNx.

Looking at the background of the study, investigators were initially concerned that omitting SLN could lead to escalation of radiation therapy.

“With a multidisciplinary team approach, we are successfully de-escalating both axillary surgery and radiation for appropriately selected low-risk patients,” Hager concluded.

Reference

Hager MG, Day CN, Corbin KS, Boughey JC. impact of omission of sentinel lymph node surgery on radiation treatment in patients age 50 and older with breast cancer treated with lumpectomy: a single-institution retrospective review. Presented at the 2026 American Society of Breast Surgeons Annual Meeting; April 29-May 3, 2026; Seattle, WA.