Abstract PD18-03: Final analysis of the Phase III PEONY trial: long-term efficacy and safety of neoadjuvant–adjuvant pertuzumab or placebo, plus trastuzumab and docetaxel, in patients with HER2-positive early or locally advanced breast cancer

Abstract BACKGROUND In the Phase II NeoSphere study (NCT00545688), dual HER2 blockade with pertuzumab (P) + trastuzumab (H), + docetaxel (D) significantly increased pathologic complete response (pCR) vs. H+D in the neoadjuvant setting for HER2-positive early breast cancer (EBC), locally advanced (LA) BC, or inflammatory BC, with supportive progression- and disease-free survival (DFS) data. Consistently, the randomized, multicenter, double-blind, placebo (Pla)-controlled Phase III PEONY trial (NCT02586025) significantly improved total pCR (tpCR; primary endpoint) with P+H+D vs. H+D in an Asian population, and safety data were in-line with the known P safety profile. We present the final analysis of long-term efficacy (at 3 and 5 years) and safety from the study. METHODS Patients had centrally confirmed HER2-positive EBC (T2–3, N0–1) or LABC (T2–3, N2 or N3; T4, any N) and were randomized 2:1 to four neoadjuvant P+H+D or Pla+H+D cycles every 3 weeks. P: 840 mg loading/420 mg maintenance doses (or Pla); H: 8 mg/kg loading/6 mg/kg maintenance; D: 75 mg/m2. Patients then received three fluorouracil, epirubicin, and cyclophosphamide cycles, followed by 13 of P+H or Pla+H in the adjuvant setting for up to 1 year. Long-term outcomes (event-free survival [EFS], DFS, overall survival [OS]; all secondary endpoints) were assessed by Kaplan–Meier methods, Cox proportional hazards models, and a two-sided log-rank test (stratified by disease category and hormone receptor status). RESULTS Data cut-off was Mar 14, 2022, and 329 patients were randomized; 219 to P; 110, to Pla. Safety populations were 218 and 110 patients, respectively. Baseline characteristics were well balanced. Most patients received the full HER2-targeted cycles. Median follow-up was 62.9 months. Long-term efficacy data are shown in the table. During the overall treatment period, 70.6% of patients in the P+H+D arm and 68.2% in the Pla+H+D arm experienced grade ≥3 adverse events (AEs); the most common (in ≥5% of patients in either arm) being neutropenia (59.2% vs. 55.5%), leukopenia (34.4% vs. 34.5%), and febrile neutropenia (5.0% vs. 3.6%). Of the most common any-grade AEs (in ≥30% of patients in either arm), diarrhea was more common in the P+H+D arm (40.8% vs. 17.3% in the Pla+H+D arm). Serious AEs were reported in 17.0% and 13.6% of patients, respectively. No primary cardiac events (heart failure [New York Heart Association grade III or IV] or significant decline of left ventricular ejection fraction) or secondary cardiac events occurred during any study periods. CONCLUSIONS Long-term efficacy endpoints (EFS, DFS, and OS) were supportive of the primary endpoint results (tpCR) and suggested a clinically meaningful improvement with P+H vs. Pla+H when administered before and after surgery for one year of anti-HER2- therapy. Safety data were in-line with the known P safety profile and generally comparable between arms, with the exception of diarrhea. PEONY adds to the totality of data showing the benefit of the P+H+D regimen in HER2-positive EBC. Table 1: Long-term efficacy data Citation Format: Zhi-Ming Shao, Da Pang, Hongjian Yang, Wei Li, Shusen Wang, Shude Cui, Ning Liao, Yong-Sheng Wang, Chuan Wang, Yuan-Ching Chang, Hwei-Chung Wang, Seok Yun Kang, Jae Hong Seo, Kunwei Shen, Suphawat Laohawiriyakamol, Zefei Jiang, Liang Huang, Haiyan Wang, François Lamour, Grace Song, Eleonora Restuccia. Final analysis of the Phase III PEONY trial: long-term efficacy and safety of neoadjuvant–adjuvant pertuzumab or placebo, plus trastuzumab and docetaxel, in patients with HER2-positive early or locally advanced breast cancer [abstract]. In: Proceedings of the 2022 San Antonio Breast Cancer Symposium; 2022 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2023;83(5 Suppl):Abstract nr PD18-03.