Researchers are studying how molecular subtypes of breast cancer may be useful in planning treatment and developing new therapies.
Most studies divide breast cancer into four major molecular subtypes:
These subtypes also appear in ductal carcinoma in situ (DCIS) [37-38].
Other less common molecular subtypes have also been described including Claudin-low.
Learn more about luminal A, luminal B and HER2 type molecular subtypes.
Triple negative breast cancers are:
There are several subsets of triple negative breast cancer. One subset is referred to as basal-like because the tumors have cells with features similar to those of the outer (basal) cells surrounding the mammary ducts. Most basal-like tumors contain p53 gene mutations [42,44].
Most triple negative tumors are basal-like and most basal-like tumors are triple negative. However, not all triple negative tumors are basal-like and not all basal-like tumors are triple negative (as shown in the figure below).
About 15 to 20 percent of breast cancers are triple negative or basal-like [39-44,49].
These tumors tend to occur more often in younger women and African-American women (more on race/ethnicity and subtypes of breast cancer) [42,47,49-50]. Some findings suggest they may also be more common among Hispanic women compared to white women [43,50].
Most BRCA1-related breast cancers are both triple negative and basal-like [42,51-52].
Triple negative/basal-like tumors are often aggressive and have a poorer prognosis (at least within the first five years after diagnosis) compared to the ER-positive subtypes (luminal A and luminal B tumors) [40,42,53]. However, after five years, this difference begins to decrease and eventually goes away [9,28].
Learn more about BRCA1 gene mutations.
Even though triple negative/basal-like tumors are aggressive, they can be treated successfully. They are usually treated with some combination of surgery, radiation therapy and chemotherapy.
These tumors cannot be treated with hormone therapy or trastuzumab (Herceptin) because they are ER-negative and HER2-negative.
Learn more about breast cancer treatment.
Learn more about breast cancer surgery.
Learn more about radiation therapy.
Learn more about chemotherapy.
While targeted therapies for triple negative/basal-like tumors do not yet exist clinical trials studying treatment options are currently underway.
Potential targets for future therapies include the epidermal growth factor receptor, aB-crystallin and androgen receptor .
Learn about research we are funding to study triple negative breast cancer.
Learn More | Current Article
Clinical trials studying treatment options for triple negative/basal-like tumors are underway.
After discussing the benefits and risks with your health care provider, we encourage you to consider joining a clinical trial.
BreastCancerTrials.org in collaboration with Susan G. Komen offers a custom matching service that can help you find a clinical trial on triple negative breast cancer.
Learn more about clinical trials.
Prevalence rates of some subtypes of breast cancer differ by race.
In studies of U.S. and British women, triple negative/basal-like tumors appear to be more common among black women (especially before menopause) compared to white women [42,47,49,50]. Some findings suggest triple negative breast cancers may also be more common among Hispanic women compared to white women [43,50].
Although the reasons for racial/ethnic differences in rates of triple negative breast cancer are not clear, lifestyle factors may play a role.
For example, some findings show African-American women tend to have lower rates of breastfeeding compared to other women, which may increase the chances of having triple negative breast cancer [54-58].
It may also be that certain reproductive and lifestyle factors protect more against ER-positive breast cancers than ER-negative breast cancers, including triple negative breast cancers.
For example, African-American and Hispanic women are more likely than white women to [54-63]:
Although these factors lower the risk of breast cancer, this benefit may be limited to ER-positive breast cancers [54,58].
So, even though African-American and Hispanic women may be more likely than white women to have these protective factors, the factors may not lower the risk of triple negative breast cancers as much as they lower the risk of ER-positive cancers.
There is even some evidence that these factors may increase the risk of triple negative breast cancers [54,55-56,62-63].
These topics are under active study.
Higher rates of triple negative/basal-like tumors may explain, to some degree, the poor prognosis of breast cancers diagnosed in younger black women.
Also, luminal A tumors, which have the best prognosis of the subtypes, occur less often in premenopausal African-American women compared to postmenopausal African-American women and compared to white women of either menopausal status .
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*Please note, the information provided within Komen Perspectives articles is only current as of the date of posting. Therefore, some information may be out of date at this time.
Triple Negative Breast Cancer
Research Fast Facts: Triple Negative Breast Cancer
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