Background: The American College of Surgeons Oncology Group Z1031 trial demonstrated that neoadjuvant endocrine therapy (NET) increased breast-conserving surgery (BCS) rates for postmenopausal patients with clinical tumor stage 2–4c estrogen receptor-positive breast cancer. We evaluated national trends in NET use in relation to the conduct of the Z1031 trial and the impact of NET on the rates of BCS. Methods: Using the National Cancer Data Base (NCDB), we identified all cT2–4c hormone receptor (HR)-positive breast cancer patients age ≥50 years from 2004 to 2012. The time intervals of pre-Z1031 (2004–2006), during Z1031 (2007–2009), and post-Z1031 (2010–2012) were examined, and adjusted analyses were performed using multivariable logistic regression. Results: Of 77,272 patients, 2294 (3.0 %) received NET. Clinical T-stage distribution was 66,885 (86.6 %) for cT2, 7318 (9.5 %) for cT3, and 3069 (4.0 %) for cT4a–c. A small but statistically significant increase in NET use was noted, from 2.7 % pre-Z1031 to 3.2 % post-Z1031; the adjusted odds ratio (OR) for NET was 1.28 [95 % confidence interval (CI) 1.13–1.45; p < 0.001] for post-Z1031 versus pre-Z1031. NET use varied by clinical T stage, increasing from 1.8 % pre-Z1031 to 2.4 % post-Z1031 in cT2 patients (p < 0.001) and from 6.3 % pre-Z1031 to 7.4 % post-Z1031 in cT3 patients (p = 0.02). Patients receiving NET were more likely to undergo BCS compared with patients undergoing primary surgery (46.4 vs. 43.9 %; p = 0.02) with an adjusted OR of 1.60 (95 % CI 1.46–1.75; p < 0.001). Conclusions: NET use has increased slowly since the Z1031 trial; however, overall use remains low. NET significantly increased the rates of BCS in patients with HR-positive clinical T2–4c breast cancer. Clinicians should consider NET use for patients with HR-positive breast cancer interested in BCS.
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