(ChemotherapyAdvisor) – Administering adjuvant trastuzumab for 1 year—currently considered standard of care—remains optimal in women with HER2-positive early breast cancer, results of two studies presented during the European Society for Medical Oncology (ESMO) 2012 Congress in Vienna, Austria concluded.

Long-awaited results from HERA, the only phase 3 randomized trial to investigate whether longer duration of trastuzumab might further improve efficacy, confirmed disease-free survival (DFS) to be comparable for patients who received 1 or 2 years of treatment (unadjusted HR 0.99; 95% CI 0.85–1.14; P=0.8588), noted Richard Gelber, PhD, of Harvard Medical School and Dana-Farber Cancer Institute, Boston, MA, and colleagues.

Overall survival (OS) was also comparable between the two arms, (HR 1.05; 95% CI 0.86–1.28; P=0.6333), as was time to distant recurrence.

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The Breast International Group trial, initiated in 2001, randomly assigned 5,102 women with HER2-positive early breast cancer after completion of primary therapy (eg, surgery, chemotherapy, and radiotherapy as indicated) to trastuzumab every 3 weeks for 1 year (n=1,552), 2 years (n=1,553), or observation.

Results of the landmark efficacy analysis presented at ESMO also noted that compared with observation, the durable benefit in DFS and OS for both 1 year and 2 years of trastuzumab therapy remained stable at 8 years of median follow-up. The primary cardiac end point was comparable between the two arms (0.96% for 2 years vs 0.83% for 1 year); however, the secondary cardiac end point was higher in the 2-year arm (7.17% vs 4.10%, respectively).

“The key message for 2012 is that 1 year of treatment with trastuzumab remains the standard of care for HER2 positive early breast cancer patients,” Dr. Gelber said. “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 (for example, pertuzumab or lapatinib) might further benefit patients with HER2-positive early breast cancer,” he noted.

The second study, instituted by the French National Cancer Institute, compared 6 to 12 months of trastuzumab in a DFS non-inferiority schema in more than 3,380 patients. Median follow-up was 42.5 months.

“The trial results are inconclusive for this non-inferiority hypothesis,” said Prof. Xavier Pivot, of the Université de Franche Comté, France. “However, despite the inconclusive result in terms of non-inferiority, the HR of 1.28 suggests a trend favoring 12 months,” he added. Subgroup analyses to determine who might benefit from 6 vs 12 months of treatment will be presented later this year.

Abstracts (LBA5_PR and LBA6_PR)