Advancing Care in Metastatic Breast Cancer

Dietmar Berger

As the most commonly diagnosed type of cancer, the devastating effects of breast cancer continue to impact families around the world.¹ It’s the fifth most frequent cause of cancer deaths globally, resulting in an estimated 685,000 deaths in 2020 alone, and a physical and emotional burden for patients and their caregivers.²

Approximately 75% of breast cancers are classified as estrogen receptor-positive (ER+),³ making it the most common type of the disease diagnosed today.⁴ In ER+ breast cancers, cancer cells in the body are fueled by a person’s own estrogen hormones,⁵ and because women and men both produce estrogen,⁶ both could be at risk for potentially developing ER+ breast cancer.

Metastatic breast cancer (MBC) refers to cancer that has spread outside the breast to another part of the body, such as the liver, brain, bones or lungs.⁷ Also known as Stage IV, this is considered the most advanced stage of breast cancer.⁷ In the U.S., between 20%-30% of patients initially diagnosed with earlier stages of breast cancer eventually develop recurrent advanced or metastatic forms of the disease.⁸ Sadly, the five-year relative survival rate for metastatic female breast cancer is only 28%.⁹

UNMET NEEDS IN MBC TREATMENT

There is currently no cure for MBC. Breast cancer cells adapt to their environment and mutate, which leads to drug resistance and disease progression over time.³ Once a person reaches the metastatic stage of breast cancer, each subsequent treatment line tends to be effective for a shorter duration than the previous line of therapy due to increasing cancer resistance.¹⁰ This commonly occurs in ER+ breast cancer.¹¹

Most endocrine therapies inhibit tumor growth by either lowering estrogen levels or blocking the estrogen from activating the estrogen receptors.¹² First-line therapy for ER+ MBC often includes anti-estrogen therapies, or endocrine therapies, in combination with cyclin-dependent kinase (CDK) 4/6 inhibitors.¹³ The clinical use of CDK4/6 inhibitors has significantly improved the prognosis of patients with hormone-receptor positive (HR+) human epidermal growth factor receptor 2 (HER2)-negative MBC.¹⁴ While these therapies are often effective early in the course of the disease, approximately 30%-50% of people treated for ER+ breast cancer develop resistance to endocrine therapies.¹³ When cancer cells become resistant to therapy and progress, patients require multiple treatment approaches over time.¹⁵

Given the complex nature of MBC, there is an urgent need for new therapies and novel ways to overcome drug resistance. Recognizing the need for new solutions, our researchers at Sanofi are investigating an approach to treating ER+ breast cancer that aims to combine estrogen receptor (ER) binding potency with an oral administration. This approach involves antagonizing and degrading the ER, resulting in inhibition of the ER signaling pathway.

COMMITMENT TO RESPONSIVE INNOVATION IN MBC

As we advance these research efforts on behalf of people living with breast cancer, we’re keenly aware of the equally important task of addressing unmet needs that go beyond treatment. While early-stage breast cancer is often a story of hope, recent surveys of women living with MBC found that more than 85% do not feel included in the “pink ribbon” breast cancer initiatives, underscoring the need for more recognition and support for those in later stages of illness.¹⁶

Over the years, healthcare providers have also expressed frustration over the significant unmet needs in breast cancer. The MBC community has voiced its collective desire for new treatment options and a better balance between potential effectiveness and impacts on quality of life.¹⁷

At Sanofi, we understand that an MBC diagnosis is a very different experience than early-stage breast cancer, and we are committed to actively working with the community to drive awareness of the realities of living with this challenging disease over its entire spectrum. Every person’s experience is unique, and our clinical research programs are designed to reflect the diverse patient populations that diseases affect. Our clinical research program in MBC, for example, was informed by eight panels and interviews involving 40 patients with diverse backgrounds.

Until we have a cure, we will continue to work toward advancing care – addressing the real needs of people living with MBC by balancing the potential for extending survival with the effects on a person’s ability to function and maintain their quality of life.

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