E13: Locoregional Therapy Patterns in Older Women with Early-Stage Hormone Receptor-Positive Breast Cancer

Trial data have demonstrated that omission of locoregional therapies in women >70 years with early-stage hormone receptor-positive (HR+)/HER-2-negative (HER-2-) breast cancer does not affect overall survival. However, hesitation persists regarding the potential downstream effects of sentinel lymph node biopsy (SLNB) omission, including a possible resultant increase in radiotherapy (RT). We examined the association between SLNB omission, RT referral rates, and RT receipt in women >70 years with early-stage HR+/HER2- disease at our institution.

Methods:

Patients >70 years with cT1-2N0 HR+/HER2- breast cancer who underwent upfront surgery between 1/2016–1/2021 were identified from our institutional database. Women with prior ipsilateral breast cancer or multifocal/multicentric disease were excluded. RT referral rates were determined by chart review. Patients were endocrine therapy (ET) “adherent” if they completed 5 years of therapy or endorsed taking ET at last clinic visit. Chi-square tests were used to compare rates over time. A multivariate logistic regression model adjusting for patient- and disease-level factors was used to assess factors associated with RT receipt.

Results:

Of 675 patients, 49.9% were 70-74 years old, 29.8% were 75-79, and 20.3% were ≥80. Only 0.04% of patients underwent mastectomy. Of the 214 patients (37.7%) who underwent SLNB, 19 (8.9%) were node-positive. RT referrals were made for 68.3% of the total population and did not change significantly over time (67.9% to 73.0%, p=0.11). Rates of RT received, however, did significantly decrease over time (49.8% to 39.8%, p=0.04). Overall, ET adherence was 60.3%, significantly higher in patients who underwent SLNB (74.3% vs 53.8%, p< 0.001). In multivariate analysis of patients undergoing lumpectomy, patients who were older, treated in later years, had lower tumor grade and stage, as well as omission of SLNB were significantly less likely to receive RT (Table). With a median follow-up of 3.8 years, there were 17 (2.5%) local recurrences (LR), no regional recurrences, and 3 (0.4%) distant recurrences. No significant difference in LR was seen by SLNB performance (2.6% vs 2.3%, p=0.8), or RT receipt (2.4% vs 2.7%, p=0.9).

Conclusions:

Despite low SLNB rates, RT referrals remained similar and RT receipt significantly decreased over the study period. LR rates did not differ by SLNB or RT receipt, suggesting that global de-escalation of locoregional therapy in older women with early-stage disease should be strongly considered in appropriate candidates.