This story is a supplement to our feature "New Breast Cancer Treatments Help Sufferers Gain Ground" which was printed in the June 2008 issue of Scientific American.

Targeted therapies will be most powerful, in principle, when they are used together in combinations tailored to the tumor features driving an individual patient’s cancer. Clinical trials to test specific drug combinations provide critical information about which treatments work most effectively on different tumor profiles and reveal unexpected interactions between drugs. But trials take time, often years, to enroll a sufficient number of participants to generate statistically significant results. That is why multinational research consortia based in Europe and the U.S. are pooling resources to conduct a 50-country trial, the Adjuvant Lapatinib and/or Trastuzumab Treatment Optimization Study (ALTTO), which has just begun recruiting in the U.S.

Some 1,500 testing sites will treat patients with early (stage I or II) breast cancers that overproduce the HER2 protein, giving them chemotherapy and either trastuzu­mab or lapatinib alone, or one of those drugs followed by the other, or both drugs together. The trial will provide the first side-by-side comparison of these HER2-targeted treatments that work by different mechanisms.

With a goal of including as many as 8,000 women on six continents, ALTTO has the potential to quickly generate results that can then be applied to patients everywhere. Moreover, this global data-sharing model can highlight differences in treatment responses or toxicity among different ethnic groups, a phenomenon observed with certain types of chemotherapy because of genetic variations that affect the way the drugs are metabolized by patients’ bodies. Having such information about the newer targeted therapies will help doctors to further personalize treatment, tailoring it to both the tumor and the patient.

—The Editors