Breast cancer is a progressive and life-threatening disease characterized by a series of stages of tumor development. Early stages of breast cancer involve the growth of a tumor within the breast, with cancer cells that begin to invade the lymph nodes around the breast. Later stage cancers involve more advanced tumor growth within the lymph nodes, and migration of cancer cells throughout the body. Stage four breast cancers occur when cancer cells circulate throughout the body and colonize within distant organs, a process called metastasis. There are a number of potential treatments for stage four metastatic breast cancers.
Hormone Therapy
One class of drugs used in hormonal therapy; known as selective estrogen receptor modulators, or SERMs, work by preventing the signaling action of estrogen, reports BreastCancer.org. When stage 4 breast cancer patients take SERMs, breast cancer cells no longer respond to circulating estrogen and tumor growth becomes halted. Another class of estrogen-inhibiting drugs are called aromatase inhibitors, which prevent the synthesis of estrogen and therefore decrease estrogen available to the tumor cells, according to BreastCancer.org. The use of SERMs or aromatase inhibitors may help treat ER+ stage four breast cancers.
Systemic Chemotherapy
In some cases, physicians may treat stage four breast cancer with systemic chemotherapy or the use of highly toxic drugs. Chemotherapy agents target rapidly diving cells, so they can effectively target breast cancer cells. Chemotherapy drugs circulate throughout the entire body, so they can attack metastatic breast cancer in a number of organs, reports BreastCancer.org.
A range of chemotherapy drugs target different essential cellular processes to kill breast cancer cells. Some chemotherapy agents prevent the action of proteins required to support cell growth, while other agents induce massive DNA damage that leads to cell death. The chemotherapeutic agents chosen for stage four breast cancer can differ on a patient to patient basis, depending on the characteristics of the cancer. Physicians may administer systemic chemotherapy in combination with hormone-based therapy for stage four breast cancer.
Tyrosine Kinase Inhibitors
One hallmark of stage four breast cancer cells includes the severe dysregulation of cell behavior. Often cancer cells will have over-activation of certain proteins that promote cell growth and allow for cancer progression. A class of proteins that play a large role in cancer development are called tyrosine kinases, which can activate a number of proliferative signals in cells, reports a study published in Breast Cancer Research in 2000. Tyrosine kinase inhibitors work by inactivating these proteins, and therefore turning off the proliferative signals in cancer cells, halting cell growth.
One type of tyrosine kinase inhibitor drug used to treat some cases of stage four breast cancer is lapatinib. lapatinib is a dual-function drug, according to the National Cancer Institute--it inhibits the function of two commonly over--active tyrosine kinases found in stage four breast cancer cases. Systemic use of lapatinib is approved to treat some forms of metastatic breast cancer.
