Neoadjuvant Chemotherapy and Endocrine Therapy for Older Patients with Estrogen Receptor Positive Breast Cancer: Comparison of Approaches.

Background: Benefits of a pathologic complete response (pCR) following neoadjuvant therapy are well established, yet outcomes for older women are understudied. We sought to examine the pCR and overall survival (OS) rates of women with estrogen receptor (ER) positive breast cancer across age groups.

Methods: Women diagnosed with cT1-4, N0-3, M0, ER+/HER2- breast cancer (2010-2018) who underwent neoadjuvant chemotherapy (NACT) or neoadjuvant endocrine therapy (NET) followed by surgery were selected from the National Cancer Database and categorized by age. Differences were tested, and Cox proportional hazards models were used to estimate the association of response with OS after adjustment for covariates.

Results: In the 43,009-patient cohort, 84.8% received NACT and 15.2% received NET. Of those aged ≥ 70 (N = 5623), 51.0% received NACT, and 49.0% received NET. Compared with younger women receiving NACT, older women were less likely to have a breast or nodal pCR [no pCR by age: 85.1% (≥ 70 years) vs 82.2% (50-69 years) vs 77.7% (< 50 years), p < 0.001]. Rates of pCR were similarly low for all women receiving NET [no pCR by age: 95.6% (≥ 70 years) vs 95% (50-69 years) vs 96% (< 50 years), p = 0.06]. After adjustment, pCR after NACT was not associated with OS for older patients, but better survival outcomes were noted for older patients achieving pCR after NET.

Conclusion: For women with ER+/HER2- breast cancer, pCR rates after NACT are lower in older women compared with younger women, and are equally low after NET for all women. However, pCR after NET is associated with improved OS among older women, unlike pCR after NACT.