Treatments include surgery, radiation, chemotherapy, hormonal therapy or a combination depending on an individual's disease. Now a new international study published in New England Journal of Medicine, and covered extensively in the news, indicates that many women with early-stage hormone sensitive breast cancer do not necessarily need chemotherapy.
The study used a gene test on tumour samples to identify women who can safely avoid chemotherapy and instead take only a drug that blocks the hormone estrogen or stops the body from making it. This is called endocrine therapy and includes drugs such as tamoxifen or aromatase inhibitors such as letrozole, anastrozole or exemestane.
"We've known for some time that many women do not benefit from the addition of chemotherapy to their endocrine therapy. As well, this test is already available for eligible breast cancer patients," says Dr. Karen Gelmon, medical oncologist and breast cancer expert at BC Cancer. "What this study has done is demonstrate in a randomized trial the value of genetic testing in treatment planning; however, oncologists still need to work with their patients to determine the best treatment plan for their individual cancer. Gene tests like this one provide additional information that can be useful to that treatment plan."
The study began in 2006 and eventually included 10,253 women ages 18 to 75, including BC Cancer patients accrued through the Canadian Clinical Trials Group. Patients affected by these new findings include women who have early-stage breast tumours measuring one to five centimetres that have not spread to lymph nodes, are sensitive to estrogen and test negative for a protein called HER2.
"All of these women are currently treated with hormone therapy to decrease the risk of relapse of the cancer in their affected breast, other breast and around the body," says Dr. Gelmon. "What this study asks is whether the addition of chemo is helpful for those patients in particular. Unfortunately, this test does not tell us anything about local recurrence of a second cancer in breast tissue."
The study used a gene test called Oncotype DX that measures the activity of 21 different genes known to be involved in cancer recurrence. It is performed on tumour samples after surgery and is generally done for early-stage disease, not more advanced tumours that clearly need chemo because they have spread to lymph nodes or elsewhere. A score of 11 to 25 (out of 100) is considered to be intermediate for risk of recurrence. This test and a similar one are available to eligible BC Cancer patients.
Data from this study also indicates that women aged 50 and younger might get more benefit from chemo depending on their gene-test results. According to Dr. Gelmon, some younger women seem to have a slightly more aggressive cancer with a similar gene-test score but more research is needed to understand why. Most breast cancers occur in women over the age of 50.
"Ultimately the decision about whether or not to use chemo is made between the oncologist and a patient based on the person's unique disease and life circumstances," says Dr. Gelmon. "No test can take that away."
More information on breast cancer including treatment options can be found here.
Communications Officer, BC Cancer
Provincial Health Services Authority
PHSA media line: 778-867-7472