With Breast Surgeon Dr Mary Ling
What is triple negative breast cancer?
Triple negative breast cancer (TNBC) is a type of breast cancer that does not have any of the 3 receptors commonly found on breast cancer cells – the oestrogen, progesterone and HER2 receptors. Receptors are molecules on the surface of cancer cells, which interact with specific proteins and hormones that allow the cancer to grow and spread.
TNBCs are not fuelled by hormones oestrogen and progesterone or the HER2 protein, therefore they do not respond to endocrine (hormonal) therapy (e.g. Tamoxifen) or targeted therapy aimed at HER2 receptors (e.g Herceptin). However they generally respond to chemotherapy.
TNBCs account for 10-20% of all breast cancers.
What are the risk factors?
Anyone can be diagnosed with TNBC, but known risk factors include:
- Younger Age: premenopausal women are more likely to be diagnosed.
- Ethnicity: black and Hispanic women are more likely to be diagnosed compared with Asian and non-Hispanic white women.
- Gene Mutation: women with BRCA1 gene mutations are more likely to develop TNBC. Approximately 75% of breast cancers diagnosed in people with a BRCA1 mutation are triple negative.
How is TNBC different?
TNBC is considered more aggressive and has a poorer prognosis than other types of breast cancer. It is more likely to spread beyond the breast and more likely to recur after treatment. Metastasis is more likely to internal organs, brain and spinal cord and lungs (and less likely to bones).
TNBC also tends to be higher grade than other types of breast cancers. The higher the grade, the less the cancer cells resemble normal healthy breast cells.
TNBCs have a higher likelihood of being found as interval cancers, which are cancers diagnosed between screening mammograms.
What is the treatment for triple negative breast cancer?
The mainstay of treatment for early stage TNBC is neoadjuvant chemotherapy followed by surgery. Radiotherapy may also be required.
Research has shown that when TNBC is treated with chemotherapy before surgery (neoadjuvant chemotherapy) and there are no active cancer cells left in the tissue removed during surgery, survival is better.
Women diagnosed with TNBC, especially under the age of 50 years, should be referred for genetic counselling and testing.
What is the prognosis?
The prognosis of TNBC depends on the stage of the cancer at diagnosis.
Generally, TNBCs have a poorer prognosis than other breast cancers, but new treatments are showing encouraging results.
TNBCs have a higher rate of recurrence than other breast cancers, with most of the recurrence detected in the 5 years after the initial diagnosis. BUT, in the longer term, the risk of recurrence may be lower compared with hormone receptor positive breast cancer.