Induction endocrine therapy in older and very old patients with breast cancer.

Abstract

e12656 Background: Management of breast cancer (BC) in older adults is complicated by a high burden of comorbidity and substantial competing mortality, increasing the risk of both overtreatment and undertreatment. In routine practice, preoperative endocrine therapy with aromatase inhibitors (AIs) is often used as a “bridging” strategy during diagnostic workup and surgical planning. Assessment of changes in proliferative activity (Ki-67) may inform subsequent treatment individualization. Methods: We conducted a retrospective single-center analysis of 152 women aged ≥75 years who underwent surgical treatment at the Loginov Moscow Clinical Scientific Center between 2015 and 2020. All patients received preoperative AI therapy during the workup period; treatment duration before surgery ranged from 2 weeks to 1 year. We evaluated clinicopathologic characteristics, type of surgery, Ki-67 based on postoperative immunohistochemistry, early oncologic outcomes (locoregional recurrence, 1-year OS and DFS), and causes of death. Categorical variables are reported as n (%) with exact 95% confidence intervals (Clopper–Pearson). For zero-eventoutcomes, the upper bound of the 95% CI was calculated. Reported 1-year OS/DFS rates were supplemented with exact 95% CIs for proportions. Results: Early-stage disease (stage I–IIa) was observed in 137/152 (90.1%; 95% CI 84.2–94.4), while locally advanced disease (stage IIb–III) accounted for 15/152 (9.9%). Tumor size ≤3.0 cm was present in 133/152 (87.5%; 95% CI 81.2–92.3). Invasive carcinoma of no special type was diagnosed in 107/152 (70.4%), and invasive lobular carcinoma in 20/152 (13.2%); all tumors were hormone receptor–positive subtypes. With respect to surgical approach, mastectomy was performed in 90/152 (59.2%; 95% CI 51.0–67.1) and breast-conserving surgery in 62/152 (40.8%; 95% CI 32.9–49.0). On postoperative immunohistochemistry, a > 62% reduction in Ki-67 was documented in 82% of cases; mean Ki-67 decreased from 30% to 17% after induction endocrine therapy. No locoregional recurrences were observed in the early follow-up period (0/152; upper 95% CI 2.4%). One-year overall survival (OS) was 140/152 (92.1%; 95% CI 86.6–95.9) and one-year disease-free survival (DFS) was 147/152 (96.7%; 95% CI 92.5–98.9). Death due to BC progression occurred in 5/152 (3.3%; 95% CI 1.1–7.5), while deaths from other causes occurred in 7/152 (4.6%; 95% CI 1.9–9.3). Conclusions: In women aged ≥75 years with hormone receptor–positive BC, preoperative induction endocrine therapy with AIs administered during diagnostic workup was associated with a marked reduction in proliferative activity (Ki-67) and favorable early clinical outcomes, with no documented locoregional recurrences. The observed mortality pattern underscores the clinical importance of competing causes of death in this age group and should be considered when determining the intensity of systemic therapy.