Systemic Therapy for Breast Cancer Patients

Systemic therapy refers to medications used to treat breast cancer that travel throughout the body. Unlike surgery or radiation, which treat a specific area, systemic therapies work to destroy cancer cells wherever they may be—both in the breast and elsewhere.

These treatments are often called “anti-cancer” medications and may be used alone or in combination, depending on your specific type and stage of breast cancer.

Systemic therapy may be used at different points in breast cancer treatment:

Neoadjuvant Therapy

• Given before surgery
• Used to shrink the tumor, making surgery easier or allowing for breast-conserving surgery
• Helps doctors see how the cancer responds to treatment
• Commonly used for higher-risk, HER2-positive, triple-negative, or larger tumors 

Adjuvant Therapy

• Given after surgery
• Aims to kill any remaining cancer cells that cannot be seen on imaging
• Reduces the risk of cancer coming back (recurrence) 

Metastatic (Stage IV) Treatment

• Used when breast cancer has spread to other parts of the body
• The goal is to control the cancer, relieve symptoms, and maintain quality of life
• Treatment is often ongoing and may change over time based on how the cancer responds

Your oncology team will discuss which approach applies to you and why.

The type of systemic therapy you receive depends on:

• The biology of your cancer (hormone receptors, HER2 status)
• The stage of cancer
• Your overall health and preferences

Hormone (Anti-Estrogen) Therapy

Used for cancers that are estrogen receptor (ER) and/or progesterone receptor (PR) positive. These medications:

• Block estrogen from fueling cancer growth or
• Lower estrogen levels in the body

Examples include:

• Tamoxifen
• Aromatase inhibitors (such as letrozole, anastrozole, exemestane)
• Ovarian suppression medications in some premenopausal patients

Hormone therapy is often taken daily by mouth for several years.

Chemotherapy

Chemotherapy uses medications that kill fast-growing cancer cells. It may be used:

• Before surgery (neoadjuvant)
• After surgery (adjuvant)
• In metastatic breast cancer

Chemotherapy is usually given:

• Through an IV
• On a schedule with treatment days followed by rest periods

Targeted Therapy

Targeted therapies focus on specific features of cancer cells.

Anti-HER2 Therapy

Used for cancers that are HER2-positive. These medications:

• Target the HER2 protein on cancer cells
• Are highly effective and often combined with chemotherapy

Examples include:

• Trastuzumab (Herceptin)
• Pertuzumab
• T-DM1 and other newer agents

Other Targeted Therapies

Some patients may receive medications that target specific cancer pathways, such as:

• CDK4/6 inhibitors
• PARP inhibitors (for patients with certain genetic mutations)

These are often taken by mouth and used in specific clinical situations.

Immunotherapy

Immunotherapy helps the body’s immune system recognize and attack cancer cells.

• Most commonly used in certain triple-negative breast cancers
• Often combined with chemotherapy
• Given through an IV

Not all patients are candidates for immunotherapy.

Systemic therapy can be given in several ways:

Intravenous (IV)

• Medication is given through a vein, usually in the arm
• Some patients may have a longer-term IV device placed:
  • PICC line (peripherally inserted central catheter
  • Port (implanted under the skin)

Your care team will help decide what is best for you.

Subcutaneous or Intramuscular Injection

• Medication is given as an injection under the skin or into a muscle
• Often quick and done during clinic visits 

Oral Medications

• Pills, capsules, or liquids taken by mouth
• Taken at home, sometimes daily
• It is important to take these exactly as prescribed

Your oncology doctor, together with a multidisciplinary care team, will decide:

• Which medication(s) are best for you
• How they will be given
• How long treatment will last

These decisions are based on:

• Your cancer type and stage
• Test results
• Your overall health
• Your personal goals and preferences

Your oncology team will review your treatment plan in detail, answer questions, and provide education and support throughout your care.