Systemic therapies are medications that are delivered to the whole body to kill cancer cells wherever they may be located. The goal of these therapies is to minimize the risk of breast cancer metastasizing or recurring. If your cancer has recurred or spread to other organs, systemic treatment will be used to kill cancer cells or control their growth. 

Systemic therapies can be administered before surgery (neoadjuvant therapy) to shrink tumors and make them easy to remove through surgery, or after surgery (adjuvant therapy). In both situations, the main objective is to destroy the unseen microscopic cancers before they start growing. This will lower the risk of distant spread of breast cancer after surgery.

The type of adjuvant systemic therapy recommended depends on;

  • Your tumor size and menopausal status
  • Whether your lymph nodes have cancer cells or not
  • Whether your tumor overproduces proteins like HER2/neu or the tumor contains hormone receptors
  • Whether you have a high recurrence score

The most commonly used systemic therapies include;

Chemotherapy

Chemotherapy is a systemic therapy that is given to a patient as adjuvant or neoadjuvant therapy. Chemotherapy is also used to treat patients whose breast cancer has metastasized or recurred. 

Chemotherapy can be administered intravenously or orally as a pill. A patient receives chemotherapy in cycles with time to recover in between treatments. The type of drug prescribed by the medical oncologist will determine how long each cycle will be. Medications can be taken daily for a week or two, or only once every two to three weeks.

Endocrine Therapy

Endocrine therapy is given to patients to block estrogen (ER) or progesterone (PR) receptors in breast cancer cells. It can also reduce the number of receptors or block ovaries from producing hormones. Endocrine therapy can also block the activity of an enzyme known as aromatase to reduce estrogen levels in the body. Endocrine therapy is given as adjuvant therapy. It comes in pill form, which is taken daily by the patient.

The type of endocrine therapy and the duration it is administered depends on your stage of breast cancer, whether you’ve reached menopause, or if you have other problems such as blood clot risk factors osteoporosis. Previous endocrine therapies received and the progression of your breast cancer are also determining factors.

Targeted Therapy

Targeted therapies attack particular abnormalities on breast cancer cells to stop cancer from growing. They can be given before or after surgery and can also treat breast cancer recurrences or metastases. Targeted therapies do not affect healthy body cells.

Targeted therapies block the signaling pathways that tell cancer cells to grow and divide. They can alter proteins in cancer cells and cause them to die. They can also prevent new blood vessels from supplying food to cancer cells or stimulate the immune system to attack or destroy cancerous cells by targeting toxins.