Published Mar 31, 2026

‘Your Friends & Neighbors’ Actress Olivia Munn, 45, Says Hormone Therapy Medication For Breast Cancer Is ‘Sometimes Exhausting’

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Hormone Therapy During Breast Cancer Treatment

Actress and breast cancer survivor Olivia Munn, 45, who has been on hormone-suppression treatment since August 2024 to prevent cancer recurrence, has admitted it’s “sometimes exhausting” taking the medication.
The TV and film star’s type of breast cancer, called hormone receptor-positive (HR+), means that the hormones estrogen or progesterone stimulate cancer cell growth, which is why HR+ cancer is typically treated with hormone therapy drugs that lower estrogen levels or block estrogen. Munn’s sub-type, luminal B, meant that her cancer was specifically estrogen-fueled.
She’s had both her breasts removed, a hysterectomy, removing her uterus, as well as surgeries to remove her fallopian tubes and ovaries. After preserving her fertility and undergoing an egg retrieval, she has since started taking hormone-suppression treatment to prevent cancer recurrence.
Hormone therapy is used for hormone receptor-positive cancers. These types of cancers are the most common types of breast cancer. Hormone receptor-positive means the cancer or tumor needs the hormones estrogen and/or progesterone to grow and flourish. Hormone therapy works by driving the estrogen levels down or blocking the estrogen’s ability to interact with the estrogen receptor on the cancer cell.
“Endocrine (hormone) 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.

“Your Friends & Neighbors” actress Olivia Munn, who has been under hormone-suppression treatment for since August 2024 to prevent breast cancer recurrence, has admitted it’s “sometimes exhausting” taking medication.

The mom of two, has been taking the drug Anastrozole (brand name: Arimidex), which works by stopping the body from producing estrogen, for nearly two years to prevent cancer recurrence—after battling hormone receptor-positive (HR+) breast cancer.

Munn, 45, beat the disease after having both of her breasts removed (double mastectomy), a hysterectomy, removing her uterus, as well as surgeries to remove her fallopian tubes and ovaries.

She told CBS News Sunday Morning in a recent interview that she’s doing well after her breast cancer fight, despite admitting “the medicine you have to take afterwards is sometimes so exhausting.”

Munn said, “With that, I think that I’m so lucky. I don’t look at it like cancer has taken these things from me or it’s unfair that I have to look over my shoulder for the rest of my life.

“I know that I’m lucky to be here and I am so lucky that I’m in this chaos and I haven’t slept in a few days and I’m exhausted. It’s a true privilege to just be alive in the world.”

Munn also expressed how her cancer journey has helped her appreciate’s the small moments in life.

“It’s not the Christmases and the birthdays and the New Years that we remember,” she told CBS. “Life happens on a Tuesday. Like, it just happens. And you cannot expect it. And so every day, you should just be so present and grateful.”

As for the medication she’s continuing to take, she explained in an Instagram post on World Breast Cancer Research Day last year, “Endocrine therapy was discovered to be effective only 20 years ago.

“It’s a hormone therapy that works to keep hormones from reaching cancer cells, which is a treatment plan I’m currently on.”

Munn began hormone suppression therapy back in the latter part of 2023. She previously told People, after beginning treatment, she started to experience medically induced menopause.

She first took Lupron (generic name leuprolide), a hormone therapy shot that aims to reduce her estrogen levels to prevent cancer from growing, but the drug made Munn feel “next-level, debilitating exhaustion,” she told People.

The side effects prompted Munn to ask for a different medication.

Munn has since been on a five-year hormone suppression plan and taking the drug Anastrozole (brand name: Arimidex) since August 2024.

It’s helpful to understand that in postmenopausal women, there is still some production of the hormone estrogen even though the ovaries have largely shut down. Drugs called aromatase inhibitors are used to block the activity of the aromatase enzyme and, therefore, stop the production of estrogen. This helps slow down the growth of tumor cells that are sensitive to estrogen.

In most premenopausal women, the ovaries produce too much aromatase for these inhibitors to work effectively. However there is some evidence of benefit of these drugs in premenopausal women if their risk of recurrence is high enough that they’re also getting chemotherapy, but the evidence is not strong, so this should be discussed with one’s doctor.

Examples of aromatase inhibitors include anastrozole (Arimidex), letrozole (Femara), and exemestane (Aromasin). All of these are in the form of pills that are taken once a day.

In an earlier Instagram post, Munn revealed the following timeline of her breast cancer journey:

January 2022 — 2 Mammograms, 2 Ultrasounds: Clear
January 2023 — Mammogram: Clear
February 2023 — Genetic Testing: 0% Chance of Genetic Cancer
March 2023 — Tyrer-Cuzik Breast Cancer Assessment Score: 37.3%
March/April 2023 — MRI+ Ultrasound + Biopsies
April 2023 — Bilateral Breast Cancer Diagnosis
May 2023 — Nipple delay, Lymph Node Dissection and Double Mastectomy
June 2023 — Egg Retrieval
September 2023 — Breast Reconstruction
November 2023 — Begin Lupron
April 2024 — Partial Hysterectomy/ Oophorectomy
August 2024 — Begin Arimidex

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Hormone Therapy: A Powerful Tool Against the Most Common Form of Breast Cancer

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.

Hormone Therapies for Breast Cancer: Aromatase Inhibitor

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

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 Therapies for Breast Cancer: mTOR Inhibitors

Olivia’s Breast Cancer Diagnosis & Journey

Munn’s breast cancer diagnosis emerged despite receiving a “normal” mammogram and testing negative for the BRCA-gene mutation, which increases your risk for breast and ovarian cancer.

At the suggestion of her OBGYN, the “X-Men” actress underwent a Breast Cancer Risk Assessment, which helps determine a woman’s probability of getting breast cancer. Her results called for additional screening, which revealed she had an aggressive form of cancer in both of her breasts.

“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.

Munn underwent genetic testing to better understand her cancer risk. Genetic tests can be as simple as a simple saliva swab or 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 your 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.

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 it is fueled by the hormone estrogen. 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.

As for the hormonal therapy drug she’s now taking, according to BreastCancer.org, Arimidex (chemical name: anastrozole), it’s “an aromatase inhibitor used to treat all stages of hormone receptor-positive breast cancer in post-menopausal women.”

As for how this drug works, the organization explains, “Arimidex works by blocking the enzyme aromatase, which turns the hormone androgen into small amounts of estrogen in the body. This means less estrogen is available to stimulate the growth or hormone receptor-positive breast cancer cells.

“Arimidex will not work on hormone receptor-negative breast cancer.”

This drug is taken to help minimize the risk of hormone receptor-positive, early-stage breast cancer recurring in post-menopausal women after surgery, as an initial treatment for hormone receptor-positive, advanced-stage breast cancer in women who are post-menopausal, and to treat advanced-stage breast cancer that has grown after tamoxifen treatment in post-menopausal women, the organization says.

Managing Recurrence Risk

“Once a patient has finished his or her active therapy for breast cancer, we will often refer to that time as breast cancer survivorship,” Dr. Erica Mayer, a breast cancer medical oncologist at Dana Farber Cancer Institute, previously told SurvivorNet.

“This is a time when patients are still being actively monitored by their treatment team, not only to ensure that they remain healthy and cancer-free in the years ahead, but also to make sure that they have recovered from any side effects of their initial treatment, and that they are pursuing healthy behaviors for example, getting regular exercise, eating a healthy diet, and keeping up with all their other routine medical care.”

Follow Your Treatment Guidelines.

“The best way to reduce your risk of recurrence with breast cancer is to follow treatment guidelines and complete the course of treatment that’s given,” says Dr. Elisa Port, a surgical oncologist specializing in breast cancer at Mount Sinai, to SurvivorNet.

“So the challenge is to work with every individual person to make sure we give her the best chance of getting through these treatments and enjoying the benefits of these treatments, which is the lowest rate of cancer coming back,” Port says.

Limit Alcohol.

Dr. Port says the other lifestyle factor that may increase one’s risk of breast cancer recurrence is heavy alcohol intake.

Eat a Healthy Diet and Exercise.

Dr. Elizabeth Comen, a medical oncologist at Memorial Sloan Kettering Cancer Center and medical advisor to SurvivorNet, notes that while exercise is well known for supporting weight loss, research shows it may also play a meaningful role in lowering breast cancer risk.

She explains that excess weight can create chronic inflammation in the body, and fat cells can produce estrogen — a hormone that, when present at high levels over a woman’s lifetime, can raise the likelihood of developing breast cancer.

Importantly, she emphasizes that physical activity doesn’t have to be extreme or strenuous to be beneficial. A light walk can also suffice.

“Exercise doesn’t have to mean suddenly training for a triathlon or doing something completely new,” Dr. Comen says.

For many patients, she adds, a cancer diagnosis can become a catalyst to prioritize their health and build sustainable habits that support their well‑being.

Maintain a Healthy Weight.

Dr. Sairah Ahmed, an associate professor in cancer medicine at the University of Texas MD Anderson Cancer Center, tells SurvivorNet that staying as physically strong as possible can make a meaningful difference for people preparing to start treatment.

“The more physically fit you are going through your cancer treatment, the fewer side effects you’ll have and the faster you’ll get back to your normal quality of life,” she explains.

She also stresses that well‑being isn’t just about the body. Emotional resilience plays a major role for both patients and the people supporting them.

“Stress control is often something that isn’t talked about enough, but there is a lot of stress — for the patient going through cancer and for the family who has to support them,” she says.