Effect of neoadjuvant chemotherapy regimen on relapse-free survival among patients with breast cancer achieving a pathologic complete response: an early step in the de-escalation of neoadjuvant chemotherapy

BACKGROUND: Patients with breast cancer who have a pathologic complete response (pCR) to neoadjuvant chemotherapy (NACT) have improved survival. We hypothesize that once pCR has been achieved, there is no difference in subsequent postsurgical recurrence-free survival (RFS), whichever NACT regimen is used. METHODS: Data from patients with breast cancer who achieved pCR after NACT between 1996 and 2011 were reviewed. RFS was estimated by the Kaplan-Meier method, and differences between groups were assessed using log-rank testing. Cox proportional hazards regression analysis adjusted for age, menopausal status, stage, grade, tumor subtype, and adjuvant endocrine HER2-targeted radiation treatment. RESULTS: Among 721 patients who achieved pCR after NACT, 157 (21.8%) were hormone receptor-positive (HR), 310 (43.3%) were HER2-amplified, and 236 (32.7%) were triple-negative; 292 (40.5%) were stage IIA, 153 (21.2%) were stage IIB, 78 (10.8%) were stage IIIA, 66 (9.2%) were stage IIIB, and 132 (18.3%) were stage IIIC. Most patients (367 [50.9%]) had been treated with adriamycin-based chemotherapy plus taxane (A + T), 56 (7.8%) without taxane (A no T), 227 (31.5%) with HER2-targeted therapy, and 71 (9.8%) provider choice. Median follow-up was 7.1 years. Adjuvant chemotherapy was employed in 196 (27%) patients, adjuvant endocrine in 261 (36%), and adjuvant radiation in the majority (559 [77.5%]). There was no statistically significant difference in RFS by NACT group. Adjusted RFS hazard ratios, comparing each treatment with the reference group A + T, were 1.25 (95% CI 0.47–3.35) for A no T, 0.90 (95% CI 0.37–2.20) for HER2-targeted therapy, and 1.28 (95% CI 0.55–2.98) for provider choice. CONCLUSIONS: These data suggest that postsurgical RFS is not significantly influenced by the choice of NACT or cancer subtype among patients achieving pCR. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (10.1186/s13058-018-0945-7) contains supplementary material, which is available to authorized users.