By Blossom Paravattil, Megan Cole, and Brandel France de Bravo, MPH
Chemotherapy can save lives, but some types of chemotherapy work better for some patients. In 2010, scientists from the European Breast Cancer Conference announced a new way to determine which breast cancer patients are likely to benefit from which chemotherapy treatments.
The scientists conducted a study called a meta-analysis that looked at four large breast cancer trials with a total of 3,000 patients. Researchers found that having a defect in chromosome 17 (called CEP17) meant that the patient’s tumor was much more likely to respond to chemotherapy drugs called anthracyclines, in comparison to those without the defect.[end Bartlett JMS, Munro A, O’Malley FP, Earle H, Poole CJ, Cardoso F, et al. Duplication of chromosome 17 CEP predicts for anthracycline benefit: evidence from an international meta-analysis of 4 adjuvant breast cancer trials for the HER2/TOP2A meta-analysis study group. 7th European Breast Cancer Conference (EBCC-7)]
Anthracyclines are antibiotics that are used to treat cancer by interfering with the enzymes involved in DNA replication. DNA tells cells how to make copies of themselves. If the DNA gets damaged, the “instructions” can contain errors, which causes cells to multiply uncontrollably, resulting in cancer.[end U.S. National Library of Medicine (2010). What is DNA? Retrieved from <http://ghr.nlm.nih.gov/handbook/basics/dna>]
The defect called CEP17 is on the same chromosome as other genes that are associated with breast cancer (such as HER-2), and a simple test known as the FISH (fluorescent in situ hybridization) can detect it. In the meta-analysis, researchers found that more than one in four breast cancer patients (27.5%) had this genetic abnormality or mutation, which is linked to poorer survival rates. The good news for women with CEP17 is that when they are treated with anthracyclines, they are about two-thirds more likely to survive and to not have a recurrence of cancer than women with CEP17 who receive other types of chemotherapy. Just as importantly, the researchers discovered that women who do not have CEP17 should not take anthracyclines, because it will not work for them.
Although there are many factors that determine whether chemotherapy will be effective, a test to measure CEP17 can help physicians choose the most effective chemotherapy to improve a patient’s chances of survival. Chemotherapy has very unpleasant side effects, and choosing the most effective chemotherapy the first time (rather than trying different types of chemotherapy until one works) helps patients fight cancer more quickly and avoid the drugs that wouldn’t improve their chances of surviving cancer. More studies are needed to better understand CEP17 and to improve treatment, but this is an important step forward.