By Sue Rochman
Clues to Cancer
By finding and measuring the molecular hints of breast cancer in the body, researchers are aiming to improve detection and treatment
By Sue Rochman
Undoubtedly every woman who has ever had a mammogram has thought to herself: There must be a better way to detect breast cancer. Fortunately, most cancer researchers agree. That’s why they’ve been investigating an array of new approaches aimed at reliably finding cancerous breast cells. The field of biomarker research has generated some of the most potentially exciting possibilities. And if these scientists are successful, discovering whether a woman has breast cancer might be as easy as finding out if she is pregnant.
A biomarker is a biological molecule or a change in a cellular process that can be measured or evaluated in blood, urine or body tissue. If a test reveals that a biomarker is present, or that it is present at an abnormal level, it can provide important information that can guide medical care. Pregnancy tests, for example, look for human chorionic gonadotropin (hCG) in urine or blood. The hormone hCG is made only when a fertilized egg implants in the uterus, which is what makes it an excellent biomarker for pregnancy. If it’s there, a woman is pregnant; if it’s not, she’s not.
Scientists have been looking for what would be the equivalent of hCG in breast cancer for more than 30 years, hoping to find a simple way to detect the disease at an early, treatable stage. “Since we first had the notion that there were things floating around in the blood that could be indicative of whether someone has cancer, finding a biomarker for cancer has been the Holy Grail,” says Jeffrey Marks, a molecular biologist in the department of surgery at Duke University, in Durham, N.C. Today, many breast cancer specialists have expanded that quest, hunting for biomarkers that could guide virtually all aspects of breast cancer care, from screening and diagnosis to treatment and recurrence.
A Biomarker History
Biomarkers have played a critical role in breast cancer treatment since the mid-1980s, when pathologists began testing tumors to learn if they had estrogen receptors and thus had the potential to respond to the drug tamoxifen. Prior to routine estrogen receptor (ER) testing, tamoxifen, which received U.S. Food and Drug Administration (FDA) approval as a breast cancer treatment in 1978, wasn’t widely used because studies hadn’t shown it to be more effective than chemotherapy. As researchers learned more about the estrogen receptors on breast cancer cells, and developed methods to test for them, they came to question whether tamoxifen might actually only be effective in tumors that were ER-positive. This led some investigators to initiate new studies that enrolled only women who were ER-positive, while other researchers re-analyzed data from older studies, taking ER status into account. These studies showed that tamoxifen was much more effective than previously believed, paving the way for more research into hormone therapies. The finding also suggested that results in past studies of other drugs may have appeared lackluster not because the drugs were ineffective, but because researchers didn’t yet know how to identify the specific tumor types that would respond to them.