ABSTRACT

Purpose. Trial data demonstrate that omission of select locoregional therapies in women ≥ 70 years with earlystage HR+/HER2− breast cancer does not afect overall survival. However, the potential downstream effects of omitting sentinel lymph node biopsy (SLNB) on rates of adjuvant radiotherapy (RT) and endocrine therapy (ET) are unclear. We examined the association between SLNB omission, RT referral rates, RT receipt, and ET adherence in this population.
Methods. Patients ≥70 years with unifocal cT1-2N0 HR+/ HER2− disease undergoing upfront lumpectomy from January 2016 to January 2021 were identifed from an institutional database. Radiotherapy referral, receipt, and ET adherence were examined by SLNB receipt. Multivariate
logistic regression adjusting for patient and disease-level characteristics was used to assess factors associated with RT receipt and ET adherence.
Results. Of 670 patients, 460 (68.7%) had SLNB omitted. Only 19 (9.0%) who underwent SLNB were node-positive. Radiotherapy referrals were made for 68.5% of patients.More patients who underwent SLNB received RT referral (90.5%), treatment (77.4%), and were ET-adherent (77.6%)
(p<0.001). On adjusted analyses, patients ≥80 years and those with SLNB omitted were less likely to receive RT and be ET adherent. There was no diference in ipsilateral breast recurrence by SLNB performance (2.6% [SLNB] vs. 2.4% [no-SLNB], p=0.86), or by RT receipt (2.7% [RT] vs. 2.4%
[no-RT], p=0.77) at a median 3.6 years.
Conclusions. Omission of SLNB is associated with a lower likelihood of subsequent RT referral, receipt, and ET adherence. Locoregional rates did not difer by SLNB or RT receipt, suggesting that global de-escalation of locoregional therapies may be considered in older candidates.