Instead of size, grade, number of lymph nodes impacted and other anatomical features of the tumor itself, many oncologists now peer at the genetic makeup of the tumor. Already, lab testing can show if cancer cells are estrogen receptor (ER) positive, meaning the cells use estrogen to promote their growth; progesterone receptor (PR) positive; hormone receptor negative or whether they have too many copies of the HER-2 gene, which promotes cell proliferation.
For each type, different medications may or may not work. For ER positive cancers, for example, drugs such as tamoxifen that block hormones can be effective, but would not work in women with hormone receptor negative cancers.
"There are some breast cancers that are very large that never spread. On the other hand, there are some patients who have very small cancers who have lots of lymph nodes involved," Sener said. "Why are those patients different? What a lot us have realized is the standard anatomical descriptions of breast cancer is inadequate."
DNA technology has already revolutionized oncologists' treatment decisions, Sener said.
"This new way of looking at breast cancer genetic has allowed us to be much more focused about the prognosis, who will respond to chemo, hormones or both," Sener said. "It's really a major advance in breast cancer technology that has emerged in the last 3 to 5 years."
"Eventually, the size of the tumor will probably be an irrelevant piece of information," he said.
There's more on breast cancer at the American Cancer Society.
SOURCES: Daniel Silver, M.D., Ph.D., assistant professor of medicine, Dana Farber Cancer Institute, Harvard Medical School, Cambridge, Mass.; Stephen Sener, M.D, past president, American Cancer Society, and chief, division of surgical oncolo
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