A DNA analysis might be able to predict the outcome of breast cancers in a more accurate and efficient manner than the conventional practice of assessing the disease by looking at the size and appearance, say a European study.

Certain changes in the patterns of DNA were able to suggest cancer prognosis and response to particular treatments, says the study where researchers analyzed the genetic makeup of 595 breast cancer tumors and compared the results to non-cancerous breast tissue.

The researchers then used algorithms to separate the tumors into eight types based on changes in the structure of the chromosomes, including deletions or amplifications of DNA. The study report was published in the latest issue of Science Translational Medicine.

Cancer specialists have increasingly relied on analyses of the DNA of breast cancer cells to determine which cancers are most likely to respond to certain treatments and which have the greatest chances of recurrence, over the years, says Dr. Stephen Sener, past president of the American Cancer Society and head of the surgical oncology division at the University of Southern California's Keck School of Medicine.

"For many years, until about the turn of this century, breast cancer was thought to be one basic disease," Sener said. "But since the human genome was elucidated, now people are working on the breast cancer genome. We're learning a lot more about how cancers develop and how they behave."

Instead of size, grade, number of lymph nodes impacted and other anatomical features of the tumor itself, many oncologists now peer at its genetic makeup. At present, lab testing is used to differentiate tumors into 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.

Each type of the tumor is treated differently. For ER positive cancers, for example, drugs such as Tamoxifen that block hormones can be effective, though these may not work in women with hormone receptor negative cancers.