(ChemotherapyAdvisor)–Extending the duration of trastuzumab treatment from 1 to 2 years does not improve patient survival rates and 1 year of treatment should remain the standard of care, reported authors of a new analysis of follow-up data from the international Phase 3 HERA (Herceptin Adjuvant) trial. The findings were reported at the 2012 CTRC-AACR San Antonio Breast Cancer Symposium (SABCS).

“Giving trastuzumab for a longer duration (two years) did not improve disease-free or overall survival compared with one year of trastuzumab treatment,” reported Martine J. Piccart, MD, PhD, chief of the medicine department at the Jules Bordet Institute in Brussels, Belgium. Dr. Piccart is president of the European Society for Medical Oncology and chair of the Breast International Group, which conducted the HERA trial with Roche.

“Importantly, the durable benefit in DFS and OS for both 1 year and 2 years of trastuzumab compared with observation remains stable at 8 years of median follow-up,” Dr. Piccart and coauthors reported.

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The international, multicenter, randomized Phase 3 efficacy trial enrolled 5,102 women diagnosed with HER2+ early-stage breast cancer. After completion of surgery, chemotherapy and radiotherapy, study participants were randomized to receive trastuzumab every 3 weeks for 1 year or 2 years, or observation.

There was no statistically significant difference between the 2-year arm compared to the 1-year arm for DFS (HR, 0.99, 95% CI, 0.85-1.14; P=0.86);  OS was also similar between both groups (HR, 1.05, 95% CI, 0.86-1.28; P=0.63), Dr. Piccart reported. 

The study’s primary cardiac endpoint, symptomatic congestive heart failure, was comparable for 2- and 1-year trastuzumab treatment-arm patients (1.0% vs 0.8%, respectively). However, the secondary cardiac endpoint (asymptomatic cardiac dysfunction) was higher after 2 years of trastuzumab treatment (7.2% vs. 4.1%).

“Most of the cardiac events occurred during trastuzumab administration, and the majority were reversible when the trastuzumab was stopped,” Dr. Piccart and coauthors noted.

“These results confirm that 1 year of adjuvant trastuzumab remains the standard of care for HER2+ early breast cancer patients,” Dr. Piccart concluded. “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.”