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.

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.

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).

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.