Extending adjuvant trastuzumab from 1 to 2 years does not significantly improve outcomes in patients with HER2 positive early breast cancer
Results from the phase III HERA trial presented during the presidential symposium of the 2012 annual meeting of the European Society for Medical Oncology (ESMO) demonstrate that one year of treatment with the targeted drug trastuzumab is as good as two years of treatment, for women with HER2-positive early breast cancer who have already received initial treatment with surgery, chemotherapy and radiotherapy as needed. Furthermore, the presented HERA results, with 8 years of follow-up, confirm the sustained and statistically significant benefit of 1 year of adjuvant trastuzumab over observation in terms of overall and disease-free survival (OS and DFS).
The HERA trial, which has been run by the Breast International Group (BIG) since 2001, is an international, multi-center, phase III randomised study including 5,102 women with early HER2-positive breast cancer. After finishing primary therapy with surgery, chemotherapy and radiotherapy as indicated, they were randomly assigned to receive trastuzumab therapy every 3 weeks for 1 year, 2 years or observation.
On the 12th of April 2012 HERA reached the target number of 725 DFS events needed for 80% power to detect a true hazard ratio (HR) of 0.80 for the comparison of 2 years versus 1 year of trastuzumab. This landmark efficacy analysis revealed that the unadjusted hazard ratio for a woman experiencing disease relapse in the 2-year treatment arm versus the 1-year arm was 0.99 (95% CI 0.85-1.14; p=0.8588). Furthermore, the overall survival rate in the two arms was comparable [HR=1.05 (95% CI 0.86-1.28; p=0.6333)].
In addition to this landmark analysis, comparing 1 or 2 years of adjuvant trastuzumab, data were also presented of disease-free and overall survival analyses for 1 year of trastuzumab versus observation with a median follow-up of 8 year. These analyses demonstrate that 1 year of trastuzumab is associated with a 24% reduction in the risk of disease recurrence (HR: 0.76, p<0.0001) and in the risk of dying (HR: 0,76, p=0.0005). Given the high percentage of patients in the observation arm that received trastuzumab after initial presentation of the HERA data (approximately 50%) in 2005, this impressive risk reduction even underestimates the true effect of adjuvant trastuzumab.
"This prolonged benefit in disease-free and overall survival of 1-year trastuzumab over no trastuzumab is remarkably impressive and reassuring to patients”, Prof. Gelber (Harvard Medical School and Dana-Farber Cancer Institute, Boston, MA, USA) said. These results show that the benefit of adjuvant trastuzumab remains over time and it is not lost after some years. As such, patients can be reassured that 1 year trastuzumab is a very effective treatment, reducing the risk of disease recurrence and death by one-quarter compared to not using trastuzumab.
While extending the duration of trastuzumab administration to 2 years did not significantly improve outcome compared with 1 year trastuzumab, ongoing trials are testing whether combining trastuzumab with other anti-HER2 agents such as pertuzumab or lapatinib might further benefit patients with HER2-positive early breast cancer. In conclusion, these results confirm that 1 year of adjuvant trastuzumab remains the standard of care for HER2-positive early breast cancer patients. It is also reassuring that the significant improvement in DFS and OS persists over time and that the incidence of cardiac endpoints remains low at a median follow-up of 8 years.
Goldhirsch A, Piccart M, Procter M et al. HERA trial: 2 years versus 1 year of trastuzumab after adjuvant chemotherapy in women with HER2-positive early breast cancer at 8 years of median follow-up. Presented at ESMO 2012, Abstract LBA6.