Olivia Munn says this breast cancer risk assessment score saved her life. Here's what to know.

Actress Olivia Munn revealed she was diagnosed with an aggressive form of breast cancer known as luminal B in February 2023, in an emotional Instagram she posted on March 13. Only two months prior to the diagnosis, the 43-year-old Daily Show correspondent and star of The Newsroom had done genetic testing and found out she was negative for the cancer-linked BRCA gene. Munn also said she recently had a normal mammogram. “I wouldn’t have found my cancer for another year — at my next scheduled mammogram — except that my OBGYN, Dr. Thaïs Aliabadi, decided to calculate my Breast Cancer Risk Assessment Score.”

Munn had a 37% risk of developing breast cancer, according to the assessment by her doctor. As a result, she went for further testing, leading to her diagnosis. Munn had luminal B tumors in both breasts. She wrote that the risk assessment “saved my life.” She’s now undergone a double mastectomy to prevent the cancer from spreading, as well as reconstructive surgery.

Here’s what to know about luminal B breast cancer, and how to assess your own risk.

What is luminal B breast cancer?

Luminal B breast cancer accounts for up to 20% of the more than 240,000 new cases of breast cancer diagnosed each year, according to the Susan G. Komen Foundation. It tends to be diagnosed in younger people, compared to other forms of breast cancer, and is more likely to develop within 10 years of giving birth.

Breast cancers can be divided into three groups, or classes: those that are fueled by the hormones estrogen or progesterone; those that are fueled by a protein called HER2; and those that aren’t sensitive to any of these hormones or HER2, known as triple negative breast cancer.

Luminal tumors are sensitive to both hormones and the HER2 protein. “Luminal A tumors are more slow growing, and tend to be very strongly hormone sensitive, versus luminal B, which are also very hormone-sensitive but may be faster growing or more aggressive,” Dr. Halle Moore, director of breast medical oncology at Cleveland Clinic, tells Yahoo Life. They also have a high risk of recurrence, so the treatment may need to be more aggressive, Moore adds.

However, because luminal tumors are sensitive to both estrogen and progesterone, as well as the HER2 protein, they can be targeted with hormone therapies, Moore says. Out of the four major subtypes of breast cancer, luminal B tumors have the second-best prognosis, with a 90.7% five-year survival rate. Triple negative cancer, on the other hand, grows more aggressively, doesn’t have good targets for treatment and is more likely to be fatal, according to the American Cancer Society.

Munn revealed that she’d undergone a double mastectomy to help reduce the chances that her cancer will spread or come back. She has not specified what kind of treatment she has received, but Moore says that patients with luminal B breast cancer typically undergo chemotherapy, hormone treatment or both to prevent recurrence. In more severe cases, patients may get radiation treatment as well.

What is the breast cancer risk assessment score Olivia Munn says saved her life?

There are several versions of breast cancer risk assessment tools that use information about your health history and your family’s history of cancer to generate a score for your approximate risk of developing breast cancer. This typically includes questions about whether and how many of your first-degree relatives — such as your mother, sisters and daughters — have had breast cancer and, if so, whether they’ve tested positive for a BRCA gene mutation or another genetic condition linked to breast cancer. Age, race and reproductive history also play a role in calculating your risk.

“The biggest risk factor for breast cancer is being female, and it turns out that the more years of circulating estrogen you’ve had, the higher the risk of breast cancer,” says Moore. “So starting your period at a younger age or going through menopause at an older age can contribute to your risk.” Pregnancy, on the other hand, has an impact on the circulation of estrogen and can reduce breast cancer risks, especially if you get pregnant for the first time when you are younger, she adds.

It's worth noting this assessment tool is only applicable for people between the ages of 35 and 85. It also won’t take into account all factors, like exposure to radiation for treatment of other conditions, which can increase breast cancer risks substantially, Moore says.

You can ask your ob-gyn or other health care provider to do a risk assessment for you, or you can try this online tool from the National Cancer Institute. The assessment tool is intended for people who do not carry the BRCA1 or BRCA2 gene mutations linked to higher breast cancer risk. While you can certainly use the tool on your own, Moore says doing it with a health care provider is a good idea, so you can come up with a plan for screening with them.

If your risk assessment score is 20% or higher, Moore says you and your health care provider might want to consider strategies to help reduce your risks, as well as extra screenings or starting screening early.

When to get screened and how to reduce your breast cancer risks

Mammograms, which take X-ray images of the breast to look for signs of cancer, are the gold standard for breast cancer screening. The U.S. Preventive Services Task Force (USPSTF) recommends that women with average risk of breast cancer start getting mammograms every other year at age 50, while the American Cancer Society (ACS) says annual mammograms should start at age 45. There's also recent research that says getting screened starting at age 40 can save lives, so it's important to talk to your health care provider about the timing of screenings.

Official guidelines caution that starting via mammograms too early might expose young women to radiation and actually increase their breast cancer risks. They also site overdiagnosis, the cost of screening (by mammography, MRI or ultrasound), the fact that mammograms are less accurate for younger, denser breasts, and concerns that it will cause undo anxiety.

Munn's own ob-gyn, and the host of the SHE MD podcast, Dr. Thaïs Aliabadi, believes more lives could be saved if more women completed risk assessments, and got more screening, earlier. "Basically every single woman needs to know their lifetime risk, even if you don't have a family history of breast cancer," she tells Yahoo Life.

It's personal to Aliabadi. Despite having no family history of breast cancer, being negative for BRCA gene mutations, having clear breast ultrasounds, never smoking and generally living a healthy lifestyle, she scored a 37% lifetime risk of breast cancer using the risk assessment tool. Aliabadi elected to undergo a preventive double mastectomy, and early-stage cancer was discovered in the removed breast tissue.

"If I had not been my own advocate, I would have needed chemotherapy, and chemo doesn't work very well for the type of cancer I had," Aliabadi says. "Patients need to be educated about this topic. What they do with that information is a personal decision but, by educating them, I can empower them to be their own health advocate."

If you’re at high risk — either based on a risk assessment score that takes into account your family and reproductive histories, or because you have tested positive for a BRCA gene variant — the ACS says you should start getting an annual mammogram and annual breast MRI at age 30. After finding out her risk score, Munn underwent both, followed by a biopsy.

Health organizations and providers don't recommend BRCA testing unless you have a higher risk, such as a family history of breast and ovarian cancer or a relative who has been diagnosed with a BRCA mutation. It's also worth noting that BRCA gene mutations are considered rare, only affecting about 0.2% of the U.S. population, according to the Cleveland Clinic. If you get tested and are negative, like Munn, that can help determine the best treatment options if you ever develop breast cancer, Moore says.

“There are some risks we can modify and some that we can’t,” such as our age and family history, she adds. But “there are things one can do that aren’t incorporated into those risk calculations, like avoiding or limiting alcohol intake and maintaining a healthy body weight and healthy, active lifestyle by exercising regularly.”