• Posted June 26, 2023

What Is Metastatic Breast Cancer & How Is It Treated?

Metastatic breast cancer can be a daunting diagnosis, but the prognosis has improved somewhat with advances in treatment.

Also known as stage 4 breast cancer, metastatic cancer is defined as the spread of disease beyond the local breast and nearby lymph nodes. More than 150,000 individuals in the United States are living with a diagnosis of metastatic breast cancer, which accounts for the majority of breast cancer deaths. According to the American Cancer Society, more than 43,000 people, mostly women, died from breast cancer in 2022.

This advanced stage of breast cancer can occur years after an original early-stage breast cancer or it may be the first presentation of breast cancer. However, the majority of patients living with metastatic breast cancer were initially diagnosed with early-stage breast cancer and took all the right steps to reduce their risk of recurrence.

Metastatic breast cancer symptoms

Breast tumor cells originating from primary breast tumor or regional lymph nodes can spread to any other part of the body, including:

• Brain
• Lungs
• Liver
• Bones
• Ovaries
• Skin

Symptoms related to metastatic breast cancer are primarily dependent on the location of the metastasis, and then on the chronic medical conditions and general health status of the patient experiencing the symptoms.

There are a number of symptom management strategies that can be used to mitigate these toxicities. These may include multidisciplinary collaborations with other specialties, including:

• Psychosocial oncology
• Palliative care
• Oncology rehabilitation

Better quality-of-life is one of the key goals for management of metastatic breast cancer that is equally shared by patients, caregivers and clinicians.

Metastatic breast cancer treatment

Breast cancer consists of three major tumor subtypes categorized according to estrogen or progesterone receptor expression (hormone receptor-positive) or ERBB2 (HER2) gene amplification. The three subtypes have distinct risk profiles and treatment strategies.

In metastatic hormone receptor-positive breast cancer, early treatment should be endocrine therapy-based, typically with incorporation of a cyclin dependent kinase (CDK) 4/6 inhibitor, such as abemaciclib (Verzenio), palbociclib (Ibrance), or ribociclib (Kisqali). After resistance develops to the available hormonal and targeted therapy options, patients transition to treatment with chemotherapy. Studies have demonstrated equivalent overall survival for sequential single-agent versus combination chemotherapy in metastatic breast cancer, with less toxicity and improved patient quality of life on single agents. HER2-positive breast cancer is often treated with initial combination of chemotherapy and HER2 targeted therapies such as pertuzumab (Perjeta) and trastuzumab (Herceptin).

When hormone receptor expression and HER2 markers are negative, this is known as triple negative breast cancer. Metastatic triple negative breast cancer is often treated with a range of chemotherapy agents and immunotherapy.

Metastatic breast cancer survival rate

Median overall survival for metastatic breast cancer varies by subtype and ranges from 2 to 5 years. Hormone receptor-positive cancers often have the best prognosis.

Additionally, factors such as presence of visceral metastases (soft tissue lesions), brain metastases and multiple metastatic sites all confer worse prognosis, whereas a better performance status, younger age at diagnosis, bone-only metastatic disease, and longer disease-free interval between initial diagnosis and development of metastatic recurrence all improve prognosis.

Advances in metastatic breast cancer

Due to advances in clinical trials and discovery of new treatments, prognosis for metastatic breast cancer continues to improve, although there is no cure. Continued research and advocacy will undoubtedly continue to advance how doctors, like myself and my colleagues at the Yale Cancer Center, can better support patients diagnosed with metastatic breast cancer.