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Triple-negative breast cancer

October 5, 2021 • read

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Triple-negative breast cancer

One in eight Canadian women will develop breast cancer during their lifetime. It’s the most common cancer in Canadian women after non-melanoma skin cancer. Breast cancer isn’t one homogeneous disease, however, and knowing which type you have is important for a few different reasons. Triple-negative breast cancer tends to be different from other forms of cancer in some very specific ways that have implications for screening and treatment. And although it accounts for only 10-15% of all breast cancers, for women with certain risk factors, it makes up a much higher proportion of the breast cancers they get. Here’s everything you need to know about triple-negative breast cancer.

What is triple-negative breast cancer?

The type of breast cells that become cancerous dictate the kind of breast cancer that you have. In the case of triple-negative breast cancer (TNBC), its cells don’t have hormone receptors for estrogen, progesterone, or for a protein called HER2 — hence the triple-negative. This might not sound important, but it has implications for your treatment options.

Triple-negative breast cancer is also notable for its aggressive growth — it tends to metastasize (spread) rapidly. Doctors sometimes refer to it as an “interval cancer” as it can appear and grow quite quickly — sometimes in the interval between breast cancer screenings. It’s also more likely to spread to other areas of the body, which makes detecting it early extremely important. TNBC causes the same symptoms as other breast cancers, so there’s no way of knowing which type you have until your doctor tests your biopsied tissue.

Who is most at risk?

Unlike most other cancers, TNBC is more common in younger women — specifically those under 40. It’s also more likely to affect Black women and women with certain genetic mutations — the BRCA2 and especially the BRCA1 gene mutation. Around one-third of BRCA1 gene carriers with breast cancer have triple-negative breast cancer.

Is triple-negative breast cancer less responsive to treatment?

Some breast cancers fuel their growth by attaching to certain hormones that your body produces — progesterone and/or estrogen. This makes hormonal therapy an effective treatment for helping to slow and even stop the growth of these cancers. TNBC cells don’t have receptors for either estrogen or progesterone, however, so hormone therapy isn’t a treatment option. This leaves surgery, radiation, and chemotherapy as the main treatments for TNBC. Immunotherapy can also be used for advanced stages of TNBC. It helps to boost the immune system so it can continue fighting the cancer. 

Triple-negative breast cancer often responds well to initial bouts of chemo. Within the first three years after diagnosis, however, it tends to recur more than other breast cancers. For this reason, doctors may recommend removing one or both breasts in order to stop the cancer’s reemergence. This isn’t the case for all patients with TNBC, however. New research shows that for those in the early stages of TNBC, combining breast-conserving therapy with chemo results in a better prognosis and less chance of recurrence than mastectomy.

In consultation with their healthcare provider, some women choose to have a double mastectomy preemptively if they carry the BRCA1/2 gene. While double mastectomy reduces the mortality risk for patients with the BRCA1 mutation, for patients with the BRCA2 gene mutation, it’s not as clear-cut. In their case, surveillance may be equally effective at reducing mortality. Because of this, women with a BRCA gene mutation benefit from individualized counselling based on their BRCA gene mutation type. 

How can I find out if I have the BRCA1/2 gene?

If you’ve been diagnosed with breast cancer or have a family history of the disease, you may qualify for genetic testing. Genetic testing lets you know whether or not you have a BRCA gene mutation, helping to determine your risk of developing breast cancer. In Canada, your doctor can refer you for genetic testing. If you fit the criteria, genetic testing is covered in almost every province and territory

What are the benefits of genetic testing?

Having access to your genetic information allows you to better make decisions about your health. Knowing whether or not you have a BRCA gene mutation may prompt you to access screening at an earlier age or more frequently than you may have otherwise. It might also give you access to screening tools beyond the usual mammogram, such as an MRI or breast ultrasound. The earlier you treat your cancer, the more likely the treatment is to work. These screening tools may help you to find out if you have cancer at an early stage of the disease. Genetic testing can also lead you to discuss preventative options with your doctor. Some women, for example, opt to have a double mastectomy if they find out that they carry the BRCA 1/2 gene. Your genetic testing can also spur other family members to get screened as well.

Triple-negative breast cancer tends to be both more aggressive and less responsive to treatment than other forms of breast cancer. You may have also heard that a diagnosis of TNBC is more likely to end with a negative prognosis. However, overall survival estimates are based on large population studies — they don’t necessarily predict what will happen in an individual’s case. Our oncology navigation experts can discuss any of your questions around TNBC, or other types of breast cancer. They can also help you determine if you’re eligible for funded Canadian genetic testing. If you’ve received a breast cancer diagnosis or want to find out more about your risk of a BRCA gene mutation, speak to one of our oncology navigation experts today.

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