Triple-negative breast cancer is different from the more common types of breast cancer. It is harder to treat and much more aggressive.

Because it is aggressive and rare, fewer treatment options are available. It also tends to have a higher rate of recurrence.

According to breastcancer.org, this form of the cancer accounts for around 10–20% of all breast cancer diagnoses.

In this article, we look at the risk factors, diagnosis, and available treatments for triple-negative breast cancer.

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Triple-negative breast cancer is aggressive and often returns after treatment.

Triple-negative breast cancer is that which tests negative for three receptors: estrogen, progesterone, and human epidermal growth factor receptor 2 (HER2). It is also the least common form of breast cancer and the hardest to treat.

To understand triple-negative breast cancer, it helps to know about the breast cancers that test positive for one or more of the receptors mentioned above. These are:

  • estrogen receptor-positive
  • progesterone receptor-positive
  • HER2 receptor-positive

Progesterone receptor-positive and estrogen receptor-positive breast cancers are the most common. Progesterone and estrogen are the two main sex hormones in women.

There are hormonal therapies available that can help treat and prevent recurrence for people who develop one of these types. In fact, many breast cancers are both estrogen- and progesterone-positive. If one type of hormone therapy does not work, another therapy often has a positive outcome.

HER2 receptor-positive breast cancer is less common. About 20% of breast cancers are HER2-positive. HER2 is the name for the gene, and HER2 is the name for the proteins it produces to stimulate growth.

HER2-positive breast cancer cells have an abundance of HER2 receptors on their surface. Like breast cancers caused by hormone receptors, different therapy options that target the HER2 receptors can help treat this type of cancer.

However, no targeted therapies are available for triple-negative breast cancer. It is also more likely than other types of breast cancer to spread and recur.

Researchers have identified the following risk factors for developing triple-negative breast cancer over other types.

Obesity and inactivity

Studies suggest that people with obesity and a higher body mass index (BMI) have a higher risk of developing triple-negative breast cancer. These categories tend to include those who are not very active.

Genetics

A 2018 study in the Journal of the National Cancer Institute identified several genes that are associated with a high risk of triple-negative breast cancer.

In particular, around 70% of breast cancers in people with a BRCA gene mutation are triple-negative.

If a doctor knows that a person has a family history of breast cancer, it can help them determine whether the person has an increased risk of developing breast cancer in the future.

Age

Individuals under 50 years of age have a higher risk of developing triple-negative breast cancer.

Race

African American and Hispanic women are more susceptible to triple-negative breast cancer.

Pregnancy

A small study from 2015 found that pregnancy-associated breast cancers affecting women up to 10 years after a pregnancy were more likely to be triple-negative than those in women who had never had a pregnancy.

Its authors explain that this may be linked to a different pattern in gene expression for women who have previously had a child. However, the sample size of this study was very small.

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A biopsy can help a doctor diagnose triple-negative breast cancer.

Diagnosis of triple-negative breast cancer starts with detection.

As with other types of breast cancer, a person may feel a small, hard bump on or near their breast. In other cases, a routine scan of the breasts may reveal an area of concern.

Upon detection of a growth, the doctor will collect tissue samples. This procedure is known as a biopsy. In many cases, the doctor will extract tissue from the suspected lump using a needle. They will then send the samples to a laboratory for further testing.

The laboratory staff will return a pathology report to the doctor, detailing the type of cells in the growth. For some people, it is benign, meaning that there are no cancer cells present. For other people, however, the report indicates that it is cancerous.

The pathology report will also highlight the type of breast cancer. A person whose cancer tests negative for the estrogen, progesterone, and HER2 receptors will receive a diagnosis of triple-negative breast cancer.

A doctor will then assign a stage to the cancer based on the findings of the biopsy and any follow-up scans. They calculate the stage based on tumor size and the spread, if any, of the cancer.

Stage 0 breast cancer has not spread from its original site in the breast. It remains confined to the ducts or lobules and is considered noninvasive. In stages 1–3, the cancer is invasive and has spread into the breast tissue. The higher the stage, the larger the original tumor or the more the cancer has spread. Note that it has not spread beyond the breast and lymph nodes at these stages.

Stage 4 cancer has spread to the organs and tissues beyond the breast, most commonly the liver, lungs, bones, or brain.

Here, learn more about how a biopsy works.

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Early treatment and diagnosis can improve the outlook for a person with triple-negative breast cancer.

Researchers describe the outlook for cancer in 5-year survival rates. The prognosis for triple-negative breast cancer is worse than that for other types of cancer. The overall prognosis depends on the stage of the cancer at diagnosis.

A 2018 cohort study that included women with breast cancer at stages 1–3 found that the overall 5-year survival rate of this type of breast cancer was 62.1%, and that disease free survival at 5 years was 57.5%.

Disease free survival means that the cancer does not return within 5 years. Cancers that doctors diagnosed at stage 3 had a worse prognosis than those they diagnosed at stages 1–2.

However, survival and overall prognosis vary from person to person. Many factors can affect a person's outlook following treatment, including:

  • when they discovered the cancer and started receiving medical treatment for it
  • the stage of the cancer and whether or not it has spread to other tissues and organs
  • how the cancer responds to treatment

Catching cancer in its earliest stages and undergoing effective treatment may help improve the prognosis.

Q:

Does triple-negative breast cancer ever come back as another type after treatment?

A:

Most often, a recurrence of breast cancer is of the same type. Occasionally, there may be a change in receptor status.

It is possible to receive a diagnosis of triple-negative breast cancer and have a recurrence later that a doctor diagnoses with a change in receptor status (for example, a change to being estrogen-positive).

However, studies looking at breast cancer recurrences that have changed receptor status have found this scenario to be rare.

Yamini Ranchod, PhD, MS Answers represent the opinions of our medical experts. All content is strictly informational and should not be considered medical advice.