APHINITY trial (BIG 4-11): A randomized comparison of chemotherapy (C) plus trastuzumab (T) plus placebo (Pla) versus chemotherapy plus trastuzumab (T) plus pertuzumab (P) as adjuvant therapy in patients (pts) with HER2-positive early breast cancer (EBC).

Abstract

LBA500 Background: In previous trials P significantly prolonged progression free and overall survival and increased pCR rates when added to T+C in pts with HER2-positive breast cancer (BC). The APHINITY trial was designed to test whether the addition of P to adjuvant T+C improves pt outcomes. Methods: Pts with adequately excised HER2-positive, pT1-3 EBC were randomly assigned to receive standard adjuvant C plus one year of either T + P or T + Pla. Eligible pts had either node-positive disease, or node-negative disease (pN0) and a tumor size of > 1.0 cm. Pts with pN0, T1b tumors with high risk features were initially eligible. The primary efficacy endpoint was invasive disease-free survival (IDFS); we assumed a 3-year IDFS of 91.8% with P and 89,.2% with Pla. Results: 4805 pts were randomized to C and T plus either P (n = 2400) or Pla (n = 2405). Baseline demographics and tumor characteristics between the arms were well balanced, with 63% and 36% of pts having node-positive and hormone receptor negative EBC respectively. P and Pla treatments were completed in 84.5% and 87.4% of patients, respectively. IDFS events occurred in 171 (7.1%) P pts and 210 (8.7%) Pla pts (hazard ratio (HR) 0.81 (95% CI 0.68-1.00), P = 0.045). Estimates of IDFS at 3 years were 94.1% and 93.2% in the P and Pla arms, respectively. The node-positive cohort had a 3-year IDFS rate of 92.0% for P compared with 90.2% for Pla (HR 0.77 (95% CI 0.62-0.96), P = 0.019). The pN0 cohort had a 3-year IDFS rate of 97.5% for P and 98.4% for Pla; HR = 1.13 (95% CI 0.68-1.86). The safety profile of P was consistent with previous trials. For the primary cardiac endpoint (heart failure or cardiac death) and secondary cardiac endpoint (asymptomatic or mildly symptomatic LVEF decline) rates were low, 0.7% vs 0.3% and 2.7% vs 2.8%, in the P and Pla arms, respectively. Diarrhea grade ≥3 was more frequent with P (9.9% vs 3.7%). Conclusions: The APHINITY trial met its primary endpoint: P significantly improved IDFS in patients with HER2-positive EBC when added to T+C. No new safety signals were identified. Clinical trial information: NCT01358877.