Triple negative breast cancer has been in the news for several years now because it has been so difficult to treat. Now it is in the news because new treatments are on the way that may change treatment protocols.
What is triple negative breast cancer (TNBC)? When pathologists look at breast cancer cells, they check them for several features including the estrogen and progesterone status and the HER2 status. In the first two, they are looking to see if the cancer cells have extra receptors for those hormones. If so, there are several hormonal treatments, such as tamoxifen, that may prevent the cancer from recurring. HER2 is a protein that all cells need, but some breast cancer cells overexpress this protein. HER2 positive tumors tend to be more aggressive, but there are therapies that target the HER2 protein receptors, thus preventing the cells from growing. The first and most famous of these is Herceptin (trastuzumab).
Triple negative breast cancer tumors are a molecular subtype with none of these characteristics. This situation is bad news for two reasons. This type of tumor, which occurs in 15-20 percent of breast cancers, tends to be aggressive, and there are no follow up treatments like tamoxifen or Herceptin that can reduce the chance of recurrence.
Promising new treatments
Now several possibilities for treating TNBC are on the horizon. Cure Today reports on a presentation Dr. Kimberly Blackwell of Duke Cancer Institute gave to over 1,000 oncologists at the 2015 Chemotherapy Foundation Symposium in November. She said that new trials will change the way she prescribes for her triple negative patients. In one Phase III trial, two types of chemotherapy were compared for metastatic breast cancer patients. Capecitabine (brand name Xeloda) was compared to eribulin mesylate (brand name Halaven).
There was no significant difference between these drugs for most of the patients, but the Halaven worked better for one sub-group—triple negative breast cancers. The difference was significant enough for Dr. Blackwell to speculate that Halaven, which is currently approved only for advanced breast cancers might work as a first-line drug for triple negative patients.
Another Phase 3 trial reported on by Dr. Blackwell looked at how two drugs worked in triple negative metastatic patients who had BRCA 1 or 2 mutations. In this trial a chemo drug called carboplatin worked better than docetaxel (brand name Taxotere). These were Phase 3 trials, which means that they are ready to apply to metastatic TNBC patients. Earlier stage TNBC patients can ask their doctors about whether the results apply to them and their treatment plan.
Even more potential treatments in the works
Other possibilities for treating TNBC are still in the research stage. Scientists have been looking for targeted therapies that might work for triple negative tumors. The process by which cells divide requires a complicated series of steps. Think of making bread. Too much salt or sugar, too high or too low a heat can lead to disastrous results. Cancer cell growth is a little like yeast dough overflowing its bowl. This overgrowth can be prevented by stepping in at several places in the process. Scientists hope that by targeting different steps in cancer’s growth they can not only stop the rapid spread of cancer cells, but prevent the cells from figuring out how to outwit a single type of treatment.
Dr. Kornelia Polyak at Dana Farber Cancer Institute is one of the scientists looking for ways to target cancer’s rapid growth. She and her colleagues have been looking at proteins involved in cell division. They have identified a type of drug call BET inhibitors which causes genes to be less active. In the research with cells in tissue samples and in animals, BET inhibitors have been most successful in triple-negative breast cancer. Phase 1 trials which test the safety of drugs are in process, and Phase 2 trials are planned.
Another type of therapy that might work for triple negative breast cancer is immunotherapy. So far trials for immunotherapy have been mainly for melanoma and lung cancer, but some breast cancer trials are underway.
When a cancer patient finds out that her type of cancer has fewer options for treatment, it is easy to get discouraged and think the worst. However, new approaches for TNBC are already in doctors’ offices with more on the way.
For further reading
Triple Negative Breast Cancer: Making Sense of Estrogen, Progesterone, and HER2 Receptor Status
[FAQs: Triple Negative Breast Cancer](http://www.healthcentral.com/breast-cancer/c/78/94483/triple-negative "FAQs" Triple Negative Breast Cancer")
Triple Negative Breast Cancer: A Reassuring Report
Baby Steps in Research that May Help IBC and Triple Negative Breast Cancer Patients
Immunotherapy: Helping the Body Attack Cancer
Inman, S. “Big Changes Coming in Treatment of Triple-Negative Breast Cancer. Cure Today, November 25, 2015. Accessed from http://www.curetoday.com/articles/big-changes-coming-in-treatment-of-triple-negative-breast-cancer January 7, 2016.
“Study identifies first potential targeted drug for triple-negative breast cancer and uncovers drug-resistance mechanism.” Dana Farber Cancer Institute, January 6, 2016. Accessed from http://www.dana-farber.org/Newsroom/News-Releases/study-ids-first-potential-targeted-drug-for-triple-negative-breast-cancer-and-uncovers-drug-resistance-mechanism.aspx January 9, 2016.