X-Men Star Olivia Munn, 45, Says She’s “Doing Well” Amid Her Ongoing Breast Cancer Journey and Adds Her Mom, 70, Just Finished Immunotherapy for Breast Cancer and Looking ‘Younger Than Ever’

Diagnosed with luminal B breast cancer in April 2023, Munn underwent a double mastectomy—a surgery that removes both breasts to eliminate cancer or reduce risk. While the procedure itself may take only a few hours, the length often depends on whether patients choose immediate reconstruction with implants or tissue transfer.

WATCH: What Happens During a Double Mastectomy?

“A double mastectomy typically takes about two hours for the cancer part of the operation,” explained Dr. Elisa Port, Chief of Breast Surgery at Mount Sinai Health System. “The real length depends on the type of reconstruction.”

Since publicly sharing her diagnosis, Munn has maintained a hopeful outlook, inspiring other women facing breast cancer.

Then, in the summer of 2025, Munn revealed her mom was diagnosed with breast cancer.

 

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“You may know that when I talk about my own battle with cancer, I bring up the Lifetime Risk Assessment test that saved my life. I never would’ve predicted it would save my mom’s life as well,” Munn said in an Instagram post.

Munn says her mom was diagnosed with stage 1 HER2-positive breast cancer.

HER2, or human epidermal growth factor 2, is a protein present on breast cancer cells. The amount of this protein can be used to classify breast cancer into different subtypes, such as HER2-positive, for those cancers that have an abundance of the protein. HER2-negative breast cancers have low-to-no levels of the HER2 protein.

WATCH: Treatment for HER2-Positive Breast Cancer

After having the support of her mom a year earlier, Munn was adamant about being there for her mom’s cancer journey.

“From my mom being there after my double mastectomy to me being there after hers. From me having to find an oncologist, to my mom and I sharing one. I can tell you this: going through cancer is really hard,” Munn said.

How Immunotherapy Impacts Breast Cancer Treatment

Immunotherapy has transformed treatment for several cancers, including triple-negative breast cancer, one of the disease’s most aggressive forms. The landmark IMpassion130 trial was the first to show that combining immunotherapy with chemotherapy could meaningfully improve outcomes for people with metastatic triple-negative disease.

“There are subtypes of breast cancer that actually are responsive to immunotherapy,” said Dr. Sylvia Adams of NYU Perlmutter Cancer Center.

WATCH: Immunotherapy and Triple Negative Breast Cancer

She notes that in newly diagnosed metastatic triple‑negative cases, adding immunotherapy to standard chemotherapy can significantly extend survival — especially for the 41% of patients whose tumors carry the PD-L1 biomarker. In that group, survival increased from 15.5 months to 25 months.

Clinical trials in earlier-stage triple-negative breast cancer have also been encouraging. When women received immunotherapy plus chemotherapy before surgery, 80% had a pathologic complete response — meaning no cancer cells were found at surgery. These results led to the approval of Keytruda (pembrolizumab) for early-stage triple-negative breast cancer, used before surgery with chemotherapy and continued afterward for patients at high risk of recurrence.

WATCH: Breast Cancer and Immunotherapy

“We hope that the addition of immune therapy to chemotherapy will translate into long-term cancer-free benefits,” said Dr. Heather McArthur, formerly of Cedars‑Sinai.

She adds that about a quarter of women respond to immunotherapy alone in the first-line setting, likely because triple-negative tumors have a unique interaction with the immune system.

It’s important to note that while immunotherapy is a proven effective treatment for triple-negative breast cancer, it remains unclear if Munn’s mother has this specific subtype of breast cancer at this time.

Olivia’s Breast Cancer Diagnosis Despite a ‘Clear’ Mammogram

Munn learned she had an aggressive form of cancer in both of her breasts after receiving a breast cancer risk assessment. She credits the cancer risk assessment for saving her life. The diagnosis was stunning because she had recently received a clear mammogram.

The Breast Cancer Risk Assessment Tool, also called the Gail Model, allows doctors to estimate a woman’s risk of developing invasive breast cancer over the next five years.

Munn says that since going public with her cancer journey, she continues to be approached by other women who are now asking their doctors about the cancer risk assessment since learning of Munn’s, including a young mother of three.

“Every time I go out, there’s at least one person…there was this woman who’s young. She has three kids, and she says because of my story, she went out and took the test and learned she has stage 0 breast cancer,” Munn explained in an Instagram story.

“We both had this moment, I know what you’re going through, but we’re so excited that you found it early,” Munn continued.

“It’s hard to explain knowing that this diagnosis that put so much fear into me has been able to be turned into something that’s saving people’s lives,” Munn told “Meet the Press” host Kristen Welker.

Since Munn shared her story publicly, the National Cancer Institute attributes an uptick in women inquiring about a cancer risk assessment to the “X-Men” actress.

How Munn Was Introduced to the Breast Cancer Risk Assessment

“I wouldn’t have found my cancer for another year – at my next scheduled mammogram – except that my OBGYN…decided to calculate my Breast Cancer Risk Assessment Score. The fact that she did save my life,” Munn said in an Instagram post.

The Breast Cancer Risk Assessment she credits for catching her breast cancer is a “statistical model that allows healthcare professionals to calculate the probability of a woman developing breast cancer over the course of their lifetime,” Dr. Ruth Oratz, breast medical oncologist, NYU Langone Health’s Perlmutter Cancer Center, clinical professor of medicine, NYU Grossman School of Medicine, tells SurvivorNet.

A 20% score suggests a higher risk of breast cancer. Munn said her mom scored 26.2% despite having a clear mammogram. Munn also had a clear mammogram before her diagnosis.

She wanted to be proactive about her health and underwent genetic testing.

Genetic tests can be as simple as a saliva swab or a blood sample. The results help your care team determine if you have a specific mutation that puts you at higher risk for cancer. The results help doctors tailor treatment and are helpful for breast cancer patients.

“I tested negative for all (different cancer genes), including BRCA,” Munn said.

The BRCA1 and BRCA2 gene mutations are among the most important genes to look for in breast cancer. Together, they are responsible for about half of all hereditary breast cancers. These genes prevent cells from dividing haphazardly and uncontrollably in a person without mutations. Mutations prevent these genes from doing their job and can allow unchecked growth of breast, ovarian, and other tissues.

However, two months after undergoing genetic testing, Munn was diagnosed with Luminal B breast cancer in both of her breasts.

According to research in “Breast Cancer,” luminal B tumors are of a “higher grade” and tend to have a worse prognosis. This type of breast cancer is estrogen-positive (ER), meaning the hormone estrogen fuels it. It can also be progestogen (PR) negative, meaning it is not fueled by progestogen. This type of breast also tends to have a higher expression of the Ki67 protein, making it grow quickly. Hormonal therapy and chemotherapy are often used to treat this type of cancer.

Luminal is one of several types and is distinguished by its molecular makeup. Other types of breast cancer include:

• Luminal A breast cancer
• Luminal B breast cancer
• Luminal B-like breast cancer
• HER2-enriched breast cancer
• Triple-negative or basal-like breast cancer

Each type has a specific, individualized molecular structure. The different types of molecular structure of breast cancer may inform the treatment path.

Munn’s Hormone Therapy

For many women diagnosed with breast cancer, the disease is fueled by hormones—specifically estrogen or progesterone. These are known as hormone receptor-positive cancers, and they represent the most common subtype of breast cancer.

“For women who have hormone-positive breast cancer, it means that they have a cancer that needs estrogen to grow,” Dr. Elizabeth Comen, medical oncologist at Memorial Sloan Kettering Cancer Center, explained to SurvivorNet.

WATCH: Understanding Hormone Therapy

Hormone therapy is designed to block or lower the hormones that help cancer cells grow. It’s a cornerstone of treatment for hormone receptor-positive breast cancer, and it plays a vital role in both treatment and prevention.

“Endocrine therapy has significant benefits in reducing the risk of breast cancer recurrence and improving breast cancer survival,” says Dr. Eleonora Teplinsky, head of Breast Medical Oncology at Valley Health System.

These therapies work in two main ways:

• Lowering estrogen levels in the body
• Blocking estrogen receptors on cancer cells so the hormone can’t fuel tumor growth

WATCH: Hormone Therapies for Breast Cancer: Aromatase Inhibitor

Types of Hormone Therapy

One widely used drug is Tamoxifen, which blocks estrogen’s ability to bind to cancer cells. It’s used not only to treat breast cancer but also to help prevent it in women with a strong family history or other risk factors.

Another class of drugs, called aromatase inhibitors, works by stopping the body from producing estrogen altogether. These are typically prescribed to postmenopausal women and include:

• Anastrozole (Arimidex)
• Letrozole (Femara)
• Exemestane (Aromasin)

All are taken as daily pills and have been shown to slow or stop the growth of estrogen-sensitive tumors.

Hormone Therapy Side Effects Can Mimic Menopause

As Munn hinted at, hormone therapy comes with side effects, and one of them can mimic menopause.

Depending on the endocrine or hormone medication, each one may have its own side effects. Typical side effects for certain types of hormone therapy drugs may include:

• Bone pain
• Joint pain
• Loss of appetite
• Nausea and/or vomiting
• Fatigue
• Constipation

What To Ask Your Doctor

If you have been diagnosed with breast cancer, you may have questions about keeping your strength through treatment. Here are a few questions to help you begin the conversation with your doctor:

• What treatment will I be receiving?
• What side effects are associated with this treatment?
• Are there steps I can take daily to help minimize these side effects?
• What physical activity routine do you recommend for me during treatment?
• Do you have recommendations for someone who doesn’t particularly enjoy exercise?
• Can you recommend a dietitian who can help me with healthy eating tips and weight maintenance?
• I’ve been having trouble sleeping. Do you have any treatment recommendations

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