Actor Olivia Munn hadn’t noticed any breast cancer symptoms and didn’t have any concerning test results. In fact, she believed she was doing everything she could to stay on top of her breast health.

But when a breast cancer risk-assessment tool triggered additional screening, she soon found herself preparing for a double mastectomy.

“I’m lucky,” the actor, then age 42, wrote on Instagram. “We caught it with enough time that I had options. I want the same for any woman who might have to face this one day.”

Since sharing her story publicly in March 2024, Munn — now age 46 — has encouraged others to learn about breast cancer risk-assessment tools. Read on to learn about her story and how risk assessments can help with early detection.

An Initial Screening

Two months before her diagnosis in February 2023, Munn had a normal mammogram. Aiming to be proactive about her health, she also underwent genetic testing.

She tested negative for inherited gene mutations (variations) in 90 genes linked to cancer. That included the two most well-known genes associated with hereditary breast cancer, BRCA1 and BRCA2.

Despite those reassuring results, Munn’s OB-GYN, Dr. Thaïs Aliabadi, used the Tyrer-Cuzick risk-assessment model. This allowed her healthcare provider to estimate her lifetime risk of developing breast cancer.

“Dr. Aliabadi looked at factors like my age, familial breast cancer history, and the fact that I had my first child after the age of 30,” Munn shared on Instagram. “She discovered my lifetime risk was at 37 percent.”

What Is the Tyrer-Cuzick Risk-Assessment Model?

The Tyrer-Cuzick model is one of several breast cancer risk-assessment tools used to estimate a person’s likelihood of developing breast cancer. The model considers factors such as:

• Age
• Family history
• Reproductive history
• Breast density
• Certain genetic factors

Doctors use these estimates to help decide whether someone may benefit from additional screening. This may include an annual breast MRI, in addition to routine mammograms.

Munn’s breast cancer risk-assessment score was 37 percent. That’s well above the 20 percent lifetime-risk threshold that many medical organizations use when recommending annual breast MRI screening for people at high risk.

Follow-Up Testing

Because Munn’s breast cancer risk-assessment score was considered high, Dr. Aliabadi recommended that she get a breast MRI.

Unlike a mammogram, which uses X-rays, a breast MRI uses magnets and radio waves to create detailed images of breast tissue. It can detect some cancers that may not be visible on a mammogram. It’s often recommended alongside routine mammograms for people at high risk.

When Munn’s breast MRI revealed suspicious areas, it was followed by an ultrasound and biopsy (a procedure in which a tissue sample is removed and examined under a microscope).

This led to her April 2023 diagnosis of bilateral luminal B breast cancer, a fast-growing subtype found in both breasts.

What Is Luminal B Breast Cancer?

Munn was diagnosed with bilateral luminal B breast cancer. “Bilateral” means the cancer was found in both breasts.

Luminal breast cancers are named because their cells have features similar to the luminal cells that line the breast ducts. Breast cancer may be classified as luminal A or luminal B.

Luminal B is a subtype of hormone receptor (HR)-positive breast cancer. This type of breast cancer is typically fueled by estrogen. It tends to grow faster and behave more aggressively than the more common luminal A subtype.

Luminal B cancer can be HER2-negative or HER2-positive. HER2 is a protein that promotes cell growth.

Although Munn has said her cancer was HER2-negative, luminal B cancer often has a high Ki-67 level. Ki-67 is a protein that helps indicate how quickly cancer cells are dividing.

According to Susan G. Komen, luminal B tumors account for about 15 percent to 20 percent of all breast cancers.

Munn’s Breast Cancer Treatment Journey

Following her breast cancer diagnosis, Munn underwent multiple surgeries and treatments. Because luminal B cancer is HR-positive, her treatment plan didn’t focus solely on removing the cancer.

It also aimed to reduce estrogen’s effects on any remaining cancer cells with hormone therapy, lowering the risk that the cancer would return.

“In the past 10 months, I have had four surgeries,” Munn shared on Instagram in March 2024. “I have learned more about cancer, cancer treatment, and hormones than I ever could have imagined.”

Hormone Suppression Therapy

Because Munn’s cancer was HR-positive, suppressing ovarian function and reducing estrogen production became an important part of her treatment plan. That is why her healthcare team put her into medically induced menopause.

Initially, Munn took an injectable medication called leuprolide, which temporarily suppresses ovarian function and reduces estrogen production. However, the side effects, particularly fatigue, were so severe that she asked her doctor if there were any other options. That conversation led to a fifth surgery.

“I have now had an oophorectomy and hysterectomy,” Munn told Vogue in May 2024. “I took out my uterus, fallopian tubes, and both ovaries.”

Following the bilateral oophorectomy and hysterectomy, Munn started taking anastrozole, an oral medication that further reduces estrogen levels in the body by blocking aromatase, an enzyme the body uses to make estrogen.

Together, the removal of her ovaries and hormone therapy help lower the risk that Munn’s HR-positive breast cancer will return.

The Impact of Sharing Her Story

Since sharing her diagnosis publicly, Munn has used her platform to raise awareness about breast cancer risk assessment. She’s also shared the importance of looking beyond routine screening alone.

“I was diagnosed with breast cancer,” she announced on Instagram in March 2024. “I hope by sharing this it will help others find comfort, inspiration, and support on their own journey.”

In the weeks that followed Munn’s announcement, thousands of other women shared their own stories about using breast cancer risk calculators to better understand their personal risk.

Through her advocacy, Munn has helped bring greater attention to personalized breast cancer screening. She’s also highlighted the importance of understanding individual risk factors when making decisions about breast health.

If you have questions about your personal risk or whether additional screening may be appropriate for you, schedule an appointment with your healthcare provider.

Join the Conversation

On MyBCTeam, people share their experiences with breast cancer, get advice, and find support from others who understand.

Have you used a breast cancer risk-assessment tool? Let others know in the comments below.