Triple-negative breast cancer, a subtype of breast cancer, takes its name from the fact that it doesn’t have the three proteins (estrogen receptors, progesterone receptors, and HER2 receptors) known to fuel the growth of breast cancer. While this type of cancer does not respond to standard hormone-lowering medications, triple-negative tumors are much less likely to recur than estrogen-positive tumors after five years.
Estimates place the number of breast cancers that are triple-negative at between 15% and 20% of all breast cancers. Triple-negative breast cancer tends to be a more aggressive form and is more frequently diagnosed in younger women and African-American and Hispanic women. It is also more likely to occur in women who carry a BRCA mutation.
In the first years following a diagnosis, survival rates are lower, compared to hormone receptor-positive cancers, but, unlike hormonal receptor-positive tumors—which are notorious for having late recurrences—triple-negative tumors are much less likely to recur after five years. While triple-negative breast cancer may be more aggressive than hormone receptor-positive breast cancer, it may also be more curable.
A number of risk factors are associated with triple-negative breast cancer, including age, family history, genetic mutations, and ethnicity. It’s more likely to occur in younger people, African Americans or Hispanics, and those with a BRCA1 gene mutation.
Family history is a risk factor for breast cancer. A number of genes have recently been discovered that can, if defective, increase the risk of getting any type of breast cancer by 20% as well as elevate the chance that a breast cancer diagnosis will be triple-negative breast cancer. The most well-studied are the BRCA genes.
Hormonal therapies (such as tamoxifen or aromatase inhibitors) and HER2-targeted therapies (such as Herceptin) are not effective for treating triple-negative breast cancer. Triple-negative tumors tend to respond better to chemotherapy than hormone receptor-positive breast cancer. For metastatic triple-negative breast cancers, an immunotherapy drug was approved in 2018 only for triple-negative breast cancer.
Breast cancers are often present in the body for several years before they are detected. Rates of growth, once they are found, varies. In a 2016 study that looked at tumor growth between diagnosis and surgery over a month-long period, triple-negative tumors grew at a rate of about 1% a day, while hormone receptor-positive tumors grew at a slower rate.
Most women successfully treated for triple-negative breast cancer will not experience breast cancer recurrence. The risk tends to be highest during the first five years following the completion of therapy and decreases steadily thereafter.
17 beta-estradiol, or 17β-estradiol, is the major estrogen in the female body prior to menopause. Postmenopausal women with higher blood levels of this estrogen have an increased risk of breast cancer.
The word mammary refers to the milk glands in the breasts. Mammals (a term that is related to the word mammary) feed their young via maternal milk glands. In humans, the female mammary glands are the breasts.
Progesterone is the other major sex hormone, in addition to estrogen, produced by the female body. Progesterone is involved in regulating the female menstrual cycle. Hormone receptor-positive breast cancer is fueled by estrogen and progesterone, while triple-negative breast cancer cells are not influenced by these hormones.
Radiation therapy, also known as radiotherapy, involves the use of ionizing radiation to kill cancer cells. It may be used to prevent cancer recurrence after a tumor has been removed in a lumpectomy or mastectomy. It can be also used to treat certain complications of brain cancer, like brain metastasis.
National Cancer Institute. Breast Cancer Risk in American Women. Updated October 3, 2019.
Siddharth S, Sharma D. Racial disparity and triple-negative breast cancer in African-American women: A multifaceted affair between obesity, biology, and socioeconomic determinants. Cancers (Basel). 2018;10(12):514. doi:10.3390/cancers10120514
Johns Hopkins Medicine. Triple-negative breast cancer.
Shimelis H, Laduca H, Hu C, et al. Triple-negative breast cancer risk genes identified by multigene hereditary cancer panel testing. J Natl Cancer Inst. 2018;110(8):855-862. doi:10.1093/jnci/djy106
Lee SH, Kim YS, Han W, et al. Tumor growth rate of invasive breast cancers during wait times for surgery assessed by ultrasonography. Medicine (Baltimore). 2016;95(37):e4874. DOI:10.1097/MD.0000000000004874
Reddy SM, Barcenas CH, Sinha AK, et al. Long-term survival outcomes of triple-receptor negative breast cancer survivors who are disease free at 5 years and relationship with low hormone receptor positivity. Br J Cancer. 2018;118(1):17-23. doi:10.1038/bjc.2017.379
Susan G. Komen Foundation. Blood estrogen levels and breast cancer risk. September 18, 2019.