The ALTTO Breast Cancer Trial

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ALTTO: Optimizing Targeted Therapy for HER2 Breast Cancer

The Adjuvant Lapatinib And/Or Trastuzumab Treatment Optimisation study, or ALTTO, is an international phase III clinical trial of two targeted therapies for HER2-positive breast cancer. HER2 is expressed at high levels in up to 25 percent of all breast cancers. Tumors that overproduce HER2 are generally more aggressive and more likely to recur than those that do not.

The medications being tested in ALTTO, lapatinib (Tykerb®) and trastuzumab (Herceptin®), target HER2 in different ways. Researchers sought to find out whether one drug is better than the other at helping women live longer without a recurrence of their disease, or if the two drugs work better together.

The ALTTO study enrolled 8,000 participants in 44 countries. Women with HER2-positive breast cancer whose tumors had been completely removed by surgery were eligible to join. (See a summary of the ALTTO protocol.)

On September 9, 2011, the leadership of ALTTO announced that the lapatinib only arm of the trial was being discontinued. The discontinuation was based on the Independent Data Monitoring Committee’s review of efficacy in the trial, which was triggered after a prespecified number of events was reached, as outlined in the study’s protocol. For more information on this modification, go to the GlaxoSmithKline press release at and the ALTTO trial website at

On June 1, 2014, ALTTO investigators presented findings of the study at the American Society of Clinical Oncology (ASCO) annual meeting.

ALTTO is sponsored by the National Cancer Institute (NCI), part of the U.S. National Institutes of Health (NIH), and GlaxoSmithKline, the maker of lapatinib, and is being coordinated by North American Breast Cancer Groups (NABCG), based in the United States, and the Breast International Group (BIG) in Brussels, Belgium.

The ALTTO trial represents a new level of international cooperation in the advancement of cancer care. ALTTO is one of the first global initiatives in which two large academic breast cancer research networks covering different parts of the world have jointly developed a study in which all care and data collection are standardized, regardless of where patients are treated.

About the Trial

  • Targeted Agents Active Against HER2-positive Breast Cancer: Questions and Answers
    (Updated: June 1, 2014) - ALTTO was a clinical trial designed to determine whether the combination of the monoclonal antibody trastuzumab (Herceptin) and the drug lapatinib (Tykerb) was more effective in treating HER2/ErbB2-positive breast cancer when combined with chemotherapy than either agent alone. Results from ALTTO did not show additional benefit from combining lapatinib and trastuzumab compared with trastuzumab treatment alone.