Findings from 6 years median follow-up in the APHINITY study confirm benefit in invasive disease-free survival (IDFS) from adding pertuzumab to standard adjuvant treatment in patients with node-positive, human epidermal growth factor receptor 2 (HER2)-positive early breast cancer. Longer follow-up is needed to fully assess overall survival (OS) benefit. No cardiac safety concerns have emerged. The results are published on 4 February 2021 in the Journal of Clinical Oncology by Prof. Martine Piccart of the Institut Jules Bordet and L'Université Libre de Bruxelles in Brussels, Belgium and colleagues.
The APHINITY, at 45 months median follow-up, showed that pertuzumab added to adjuvant trastuzumab and chemotherapy significantly improved IDFS (hazard ratio [HR] 0.81; 95% confidence interval [CI] 0.66 to 1.00, p = 0.045) for patients with early HER2–positive breast cancer, specifically those with node-positive or hormone receptor–negative disease. A first preplanned interim analysis for OS was performed at the time of primary analysis (HR 0.89; 95% CI 0.66 to 1.21, p = 0.47) with a median follow-up of 45 months. The study team now report the preplanned second interim OS and preplanned descriptive updated IDFS analysis with 74 months median follow-up.
After surgery and central HER2-positive confirmation, 4,805 patients with node-positive or high-risk node-negative breast cancer were randomly assigned to either 1-year pertuzumab or placebo added to standard adjuvant chemotherapy and 1-year trastuzumab.
This interim OS analysis comparing pertuzumab versus placebo did not reach the p = 0.0012 level required for statistical significance (p = 0.17, HR 0.85). Six-year OS were 95% versus 94% with 125 deaths (5.2%) versus 147 (6.1%), respectively.
IDFS analysis based on 508 events in intent-to-treat population showed a HR 0.76 (95% CI 0.64 to 0.91) and 6-year IDFS of 91% and 88% for pertuzumab and placebo groups, respectively. The node-positive cohort continues to derive clear IDFS benefit from pertuzumab (HR 0.72 [95% CI 0.59 to 0.87]), 6-year IDFS being 88% and 83%, respectively. Benefit was not seen in the node-negative cohort. In a subset analysis, IDFS benefit from pertuzumab showed a HR 0.73 (95% CI 0.59 to 0.92) for hormone receptor-positive disease and a HR 0.83 (95% CI 0.63 to 1.10) for hormone receptor-negative disease.
Primary cardiac events remain <1% in both treatment groups. No new safety signals were reported.
The authors concluded that the second interim analysis of OS in the APHINITY study did not demonstrate a statistically significant OS benefit from adding pertuzumab to standard chemotherapy plus trastuzumab in HER2-positive early-stage breast cancer; the number of OS events still remains relatively low.
The benefits of dual HER2 blockade using pertuzumab and trastuzumab in the adjuvant setting for patients with node-positive disease observed at the primary analysis are reinforced in the updated analysis of IDFS. There is no evidence to justify the routine use of adjuvant dual anti-HER2 treatment for patients with node-negative early breast cancer. The longer-term benefit of pertuzumab may not depend on the hormone receptor status of the primary tumour.
The authors underlined that continued follow-up of patients is important to fully assess OS benefit at the time-driven third interim OS analysis planned for 2022 and the event-driven final OS analysis planned when 640 deaths have occurred.
The study was supported by F. Hoffmann-La Roche Ltd/Genentech.
Piccart M, Procter M, Fumagalli D, et al. Adjuvant Pertuzumab and Trastuzumab in Early HER2-Positive Breast Cancer in the APHINITY Trial: 6 Years' Follow-Up. Journal of Clinical Oncology; Published online 4 February 2021. DOI: 10.1200/JCO.20.01204.