Therapeutic Targets

A targeted therapy is one that is designed to treat only the cancer cells and minimize damage to normal, healthy cells. Cancer treatments that “target” cancer cells may offer the advantage of reduced treatment-related side effects and improved outcomes.

Conventional cancer treatments, such as chemotherapy and radiation therapy, cannot distinguish between cancer cells and healthy cells. Consequently, healthy cells are commonly damaged in the process of treating the cancer, which results in side effects. Chemotherapy damages rapidly dividing cells, a hallmark trait of cancer cells. In the process, healthy cells that are also rapidly dividing, such as blood cells and the cells lining the mouth and GI tract are also damaged. Radiation therapy kills some healthy cells that are in the path of the radiation or near the cancer being treated. Newer radiation therapy techniques can reduce, but not eliminate this damage. Treatment-related damage to healthy cells leads to complications of treatment, or side effects. These side effects may be severe, reducing a patient's quality of life, compromising their ability to receive their full, prescribed treatment, and sometimes, limiting their chance for an optimal outcome
from treatment.

The idea of matching a particular treatment to a particular patient is not a new one. It has long been recognized, for example, that hormonal therapy for breast cancer is most likely to be effective when the breast cancer contains receptors for estrogen and/or progesterone. Testing for these receptors is part of the standard clinical work-up of breast cancer. What is new, however, is the pace at which researchers are identifying new tumor markers, new tests, and new and more targeted drugs that individualize cancer treatment. Tests now exist that can assess the likelihood of cancer recurrence, the likelihood of response to particular drugs, and the presence of specific cancer targets that can be attacked by new anti-cancer drugs that directly target individual cancer cells.

Hormones are naturally occurring substances in the body that stimulate the growth of hormone sensitive tissues, such as the breast or prostate gland. When cancer arises in breast or prostate tissue, its growth and spread may be caused by the body’s own hormones. Therefore, drugs that block hormone production or change the way hormones work, and/or removal of organs that secrete hormones, such as the ovaries or testicles, are ways of fighting cancer. Hormone therapy, similar to chemotherapy, is a systemic treatment in that it may affect cancer cells throughout the body.