New Research Predicts Breast Tumor Treatment Response

?Scientists and researchers are now able to identify distinct cancer cell signatures that could help predict which women are likely to benefit from estrogen-lowering therapy.

Researchers from the Washington University School of Medicine in St. Louis have found they can “decode” the DNA of patients with advanced breast cancer to help identify distinct cancer cell "signatures" that could help predict which women are most likely to benefit from estrogen-lowering therapy, and prevent other patients from having to undergo unnecessary treatments.

In their report published June 10 in the advance online edition of Nature, the researchers discovered cell mutations that can indicate whether or not a patient will respond to aromatase inhibitors, a class of drugs designed to shrink breast tumors prior to surgery. The cell mutations are also liked with some of the clinical signatures of breast cancer tumors, giving physicians an indication of how quickly they might grow and spread.

The study examined the DNA codes from 77 post-menopausal women diagnosed with stage 2 or 3 estrogen-receptor-positive breast cancer. All of the women were prescribed aromatase inhibitors to lower the estrogen in their bodies in the hopes of reducing the size of their breast tumors. Although the inhibitors helped many women to qualify for
breast-conserving surgery instead of full-blown mastectomies, but the aromatase inhibitors do not work for all women, and the reason for that is still unknown.

The scientists discovered that tumors in women who did respond to the aromatase inhibitors had fewer cell mutations, and those who were resistant to the inhibitors had more tumors and genes with higher mutation rates and were more complex. A few of the
genes had already been recognized as important in breast cancer but some other genes involved were completely unexpected in breast cancer research, although some had been recognized for their links to leukemia. The research team concluded that because breast cancer is so common today, many mutations that occur only very infrequently can still affect thousands of women, and only with more genomic studies will physicians and cancer specialists to determine if they might they also have a role in treatment responses.

Oncologists already know that many “estrogen-receptor-positive” breast cancers can also be treated with existing drugs that have already been approved for tumors other than those in the breast cancers. The upside is that similar studies may very well provide new pathways for developing new breast cancer treatments based on each tumor's particular genomic signature instead of treatment based on where the tumors are located in a patient’s body. The scientists acknowledge that because they are only just now beginning to see that a large number of patients only have genetic mutations that occur in very low numbers throughout the population, the mutations could be the focus of new clinical trials that will identify more mutations and the drugs that are able to treat them most effectively.