Abstract P2-12-01: Survival Outcomes after Pathologic Complete Response with Neoadjuvant Endocrine Therapy vs. Neoadjuvant Chemotherapy
Chanenchuk, T; Thomas, SM; Botty van den Bruele, A; Chiba, A; Modell Parrish, KJ; Woriax, HE; DiNome, ML; Westbrook, KE; Plichta, JK
Published in: Clinical Cancer Research
Background: Neoadjuvant systemic therapy has emerged as the standard of care for many patients with breast cancer potentially leading to surgical downstaging and providing insight into treatment response and prognosis. Neoadjuvant therapies can result in pathologic complete response (pCR), which is predictive of long-term outcomes; patients who attain pCR are consistently found to have better survival outcomes than those with residual disease. Select patients with estrogen receptor positive (ER+) tumors may receive either neoadjuvant chemotherapy (NAC) or neoadjuvant endocrine therapy (NET). Although the role of NAC has been well established for various breast cancer subtypes, NET has become a more appealing option for patients with ER+ disease. As such, we sought to assess survival outcomes in those with early-stage ER+ breast cancer who received either NET or NAC, and achieved pCR. Methods: All patients diagnosed with ER+/HER2- stage I-III breast cancer in 2010-2021, who received neoadjuvant therapy followed by surgery, and achieved pCR, were selected from the National Cancer Database. Patients were stratified by type of neoadjuvant systemic therapy: NAC vs NET. The Kaplan-Meier method was used to estimate overall survival (OS) and log-rank tests were used to test for differences in OS between groups. Cox Proportional Hazards models were used to estimate the association of NAC vs NET with OS, after adjustment for demographics, disease characteristics, surgery, radiation and immunotherapy; hazard ratios (HRs) and 95% confidence intervals (CIs) are reported. Results: We identified 3313 patients meeting eligibility criteria: 3148 received NAC and 165 NET. The median follow-up for the entire cohort was 82 months. Patients who received NAC were significantly younger [median age (IQR): NAC 49y (41-58) vs NET 64y (57-69); p<0.001], more likely to have a comorbidity score of 0 (NAC 89.3% vs NET 81.2%, p=0.004), and more likely to have private insurance (NAC 68.9% vs NET 44.2%, p<0.001). There were no significant differences between the NAC and NET patients based on race/ethnicity, income level, education level, or community type (all p>0.05). Expectedly, NAC patients were more likely to have larger tumors [median tumor size (IQR): NAC 3 cm (2-4.3) vs NET 1.3cm (0.7-2.8); p<0.001), ductal histology (NAC 92.6% vs 81.2%, p<0.001), and grade 3 tumors (NAC 70.2% vs 10.3%, p<0.001), while NET patients were more likely to have T1 (NAC 22.1% vs NET 67.9%, p<0.001) and N0 disease (NAC 46% vs NET 95.8%, p<0.001). The median time from start of treatment to surgery was 159 days for the NAC cohort, and 147 days for the NET cohort (p=0.23). In the unadjusted Kaplan-Meier analysis, there was no significant difference in OS between NAC vs NET [5-year OS: NAC 0.935 (95% CI 0.926-0.944) vs NET 0.916 (95% CI 0.856-0.951); log-rank p=0.08]. After adjustment for demographics, disease characteristics, and other treatments, there was no association between OS and the study groups (NAC vs NET; p=0.63). Conclusions: Patients with ER+/HER2- early-stage breast cancer who achieved pCR had similar overall survival, regardless of whether they were treated with NAC or NET. As such, pCR appears to have similar prognostic value regardless of the type of systemic therapy used to obtain this favorable outcome.Citation Format: Tori Chanenchuk, Samantha M. Thomas, Astrid Botty van den Bruele, Akiko Chiba, Kendra J. Modell Parrish, Hannah E. Woriax, Maggie L. DiNome, Kelly E. Westbrook, Jennifer K. Plichta. Survival Outcomes after Pathologic Complete Response with Neoadjuvant Endocrine Therapy vs. Neoadjuvant Chemotherapy [abstract]. In: Proceedings of the San Antonio Breast Cancer Symposium 2024; 2024 Dec 10-13; San Antonio, TX. Philadelphia (PA): AACR; Clin Cancer Res 2025;31(12 Suppl):Abstract nr P2-12-01.
