Thousands of women diagnosed with the most common type of breast cancer can now skip chemotherapy and still have the same outcome, according to a new study presented this week.

The long-awaited study, presented at the American Society of Clinical Oncology meeting over the weekend in Chicago, confirmed what many breast cancer specialists, including those at the James Graham Brown Cancer Center at the University of Louisville, had already believed.

For women with this common type of cancer - early stage estrogen-receptor positive - anti-estrogen treatment alone provide the same benefit as chemotherapy, without the harsh and sometimes devastating side effects. Chemotherapy can cause hair loss, a weakened immune system and heart problems, among other issues. Breast cancer is the most common cancer in women worldwide.

“The name of the study is TAILORx, which is perfect, because what this means is that for a large group, treatment can be truly tailored to a woman’s circumstances,” said Elizabeth Riley, M.D., FACP, a breast cancer expert at UofL’s Brown Cancer Center and deputy director of the center. “We now have solid data that chemotherapy is not needed for many in this group and helps validate what many specialists already knew.

“For years, physicians made treatment decisions solely based on a woman’s stage of breast cancer. TAILORx now confirms the biology of the tumor may be more important. This study should reassure a woman with very early stage, estrogen-driven breast cancer that chemotherapy can be avoided without increasing her risk of breast cancer,” Riley said.

The study, published Sunday in the New England Journal of Medicine, analyzed how well a widely used genetic test called the Oncotype DX Breast Recurrence Score assessed the risk of breast cancer returning. The Oncotype DX test looks at 21 genes linked with a likelihood of recurrence. The test has a range between 0 and 100, and determines whether these genes are turned off or on, or are over expressed.

The study’s lead author, Joseph Sparano M.D., associate director for clinical research at the Albert Einstein Cancer Center and Montefiore Health System in New York City, said the data confirms women can be spared “unnecessary treatment if the test indicates chemotherapy is not likely to provide benefit.”

Riley noted there are multiple types of breast cancer, with multiple genes involved in the growth of tumors. She said those patients who will benefit from the study’s findings are estrogen sensitive, test negative for HER2 (human epidermal growth factor receptor 2), a gene that can play a role in the development of breast cancer, and have early-stage tumors below 5 centimeters that have not spread to lymph nodes.

They also have what is considered an intermediate score on the OncotypeDX test, one between 11 and 25.

Riley said that past research has shown women with scores between 0 and 10 could safely forego chemotherapy, while those with scores over 25 were best treated with a combination of chemotherapy and anti-estrogen hormonal treatment, as the cancer recurrence risk in this group was high.

“There have been clear guidelines on treatment for woman with a high or low score OncotypeDX score. It was the group in the intermediate range, from 11 to 25, that the degree of benefit of chemotherapy was not well established,” Riley said.

The study followed over 10,000 women diagnosed with breast cancer between 2006 and 2010. Of those, 6,711 had intermedia scores between 11 and 25. That group was split into two: one receiving hormone therapy and chemotherapy, and the other only hormone therapy.

The women were followed for an average of nine years, and researchers found the outcome in recurrence and survival was virtually the same.

“If you are seen by a doctor tomorrow and have a low to intermediate score on the test, you should expect not to be offered chemotherapy, unless you are under the age of 50,” Riley said.

That is the caveat, she said. Breast cancer in younger women is biologically different, and typically comes with a poorer prognosis. In premenopausal women and those younger than 50, the TAILORx results suggested that hormonal therapy alone may not be enough and chemotherapy may still be needed, she said.

While these patients should discuss their options with their doctor, they would be likely candidates for the more aggressive combination therapy, she said.

“In that case, the treatment decisions are going to depend on more than just the test, such as a thorough analysis of a patient’s particular tumor type. We can’t say that everyone under 50 needs chemotherapy, but future studies may be necessary to interpret the test in this age group,” Riley said.

Breast cancer in younger women is a focus of Riley’s. At the Brown Cancer Center, she also leads the HER Breast Cancer Program, which addresses the challenges this group faces with regional experts in the management of breast cancer in young women. The program also addresses the impact of treatment on fertility, the patient’s young children, and her career. HER stands for Hope, Empower and Restore.