What does a Medical Oncologist mean when we render the diagnosis of triple negative breast cancer? Once a patient has a biopsy with confirmed breast cancer, further tests are performed on the cancer to detect the presence of receptors on the cancer cells. What are receptors? These proteins are located in or on the cancer cells. We evaluate for three receptors, which are estrogen receptors, progesterone receptors, and HER2/neu. If cancer cells lack estrogen and progesterone receptors and don’t express too much HER2/neu, then we categorize these breast cancers triple negative and denote them as ER-/PR-/Her2-.
Because these tumors do not express estrogen or progesterone receptors, hormonal therapies are not an option. In addition, since HER2/neu is not increased, therapy in the form of monoclonal antibodies that target HER2/neu is not beneficial as well. Since there are no receptors for targeted therapies, patients will likely receive chemotherapy for treatment of their disease.
Approximately, 15-20 percent of all breast cancers diagnosed in the U.S. are triple negative breast cancers. It tends to occur in younger women, African American women, and women who have BRCA1 gene mutations. Given the predilection for this type of cancer to harbor the BRCA1 mutation, any patient with triple negative disease should be referred to a genetic counselor to undergo germline testing.
Typically, these tumors present aggressive with rapid growth of the mass. Patients with triple negative breast cancer have a worse prognosis when compared to patients with other subtypes. In a 2012 study by Lin et al. of 12,902 women, compared to women who were positive for any of the three receptors, triple negative breast cancer demonstrated worse overall survival. The poorer prognosis is attributed to the biologic characteristics of the disease, which we do not fully understand at this point. Our most recent data from the Mississippi Cancer Registry from years 2010 to 2013, demonstrate that 1234 women were diagnosed with triple negative breast cancer in the state of Mississippi.
The good news is that clinical trials are ongoing and searching for better therapies. Three ongoing trials are investigating the use of another chemotherapeutic agent, carboplatin. Results of these trials are promising but currently we are awaiting progression-free survival and overall survival data.