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Treatments & Side Effects

Systemic Therapy

Systemic therapies, unlike the localized therapies, surgery and radiation, are delivered to the entire body. Like radiation, they can be used as primary therapy (often in stage IV disease), or can be used in addition to the primary therapy of surgery.  This can be done before surgery (“neoadjuvant”), or after surgery (“adjuvant”).  Studies show that neoadjuvant and adjuvant treatments are equally effective at preventing breast cancer from recurring.  Your physician may recommend neoadjuvant treatment in the case of a large tumour, or lymph node involvement, to help achieve a successful surgery.  The current systemic therapies for breast cancer include chemotherapy, hormonal therapy and targeted therapies. 

Chemotherapy

Chemotherapy uses medications to damage and destroy cancer cells. In early stage breast cancer, chemotherapy may be given after surgery to eliminate any remaining cancer cells and reduce the risk of recurrence; sometimes chemotherapy may be given before surgery to shrink the tumour to an operable size.  In metastatic breast cancer, chemotherapy is given to shrink or slow the growth of tumours or to ease symptoms of the cancer itself. Many breast cancer patients respond well to chemotherapy.  There are many different chemotherapy drugs and drug combinations.  You and your doctor will make decisions about chemotherapy based on the type of cancer and factors in the pathology report.

Endocrine therapy 

Estrogen and progesterone can stimulate the growth of HR+ breast cancers, so hormonal therapy is used to block their action.  These therapies are used to:

  • block estrogen or progesterone receptors on the breast cancer cells, or
  • reduce the number of receptors, or
  • block the ovaries from producing hormones, or
  • block the actions of an enzyme, aromatase, which in turn lowers the level of estrogen in the body.

The choice of hormonal therapy for breast cancer and the length of time it is given depends on many factors, including whether menopause has been reached, the stage of breast cancer, other health problems (such as osteoporosis or blood clot risk factors) that may prevent taking certain types of hormonal therapy, other hormonal therapies previously taken, and disease progression.

Targeted therapy 

Targeted therapies target certain parts of cancer cells that make them different from other cells in order to selectively kill or stop them from growing.  In general, they work to:

  • Stop the growth and division of cancer cells by blocking the signaling pathways that tell them to grow
  • Alter the proteins of the cancer cells so they will die; prevent new blood vessels from feeding the cancer cells
  • Stimulate the immune system to attack the cancer cells
  • Destroy the cancer cells by carrying a toxin to only to them.

Support Medications

Support medications are drugs given to counteract the side effects of your cancer or its treatment.  Please refer to our side effects section to learn more about treatment side effects and possible treatments to manage them.

Understanding Biosimilars 

A medication such as Herceptin is made from biological materials, including cells and antigens. Often biologic medicines are large, complex molecules or a mixture of molecules. Conventional drugs are generally made through chemical synthesis, which means that they are easy to replicate and create a generic form of that drug. Because of the complexities of the biologic medicines and the living systems used to produce them, it is very difficult to replicate them. A biosimilar, or subsequent entry biologic, is the “generic” version of a biologic. It isn’t an exact replica because of the complexity of the original drug, but it’s similar.  The use of biosimilar agents for the treatment of breast cancer is currently not standard in Canada, however this may change in the near future.

What to do if drugs aren’t covered

See the Living with Breast Cancer or Living with Metastatic Breast Cancer sections of this website for details.

Systemic therapies play an important role in the treatment of breast cancer.  It’s important that you understand the risks and benefits of these valuable treatments.  If you’re uncertain, be sure to ask your healthcare team for information.

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