Prostate Cancer

Immunotherapy

An emerging treatment for prostate cancer

Immunotherapy is an innovative, evolving treatment method for cancer. This type of therapy activates the immune system to fight cancer throughout the body, using the body’s own immune cells to attack the disease.

History of immunotherapy

Immunotherapy is a cancer treatment more than 100 years in the making, beginning most notably with Dr. William B. Coley, who worked with patients and doctors to study how cancer tumors reacted to bacterial infections. He treated cancer patients with inoperable tumors by injecting a combination of bacteria, which became known as Coley’s Toxins, directly into their tumors. His results showed that this kind of treatment shrank the tumors and sometimes even cured the patient.

How the immune system works

The immune system is a group of organs, specialized cells and substances that protect the body from infection and disease. The immune system recognizes all substances normally found in the body by proteins on the surfaces, called antigens. When certain immune cells find a substance they do not recognize (because of the foreign antigens on its surface) they see that substance as harmful and then they attack it (see Figure 1). To help the body more fully recognize the invader, some immune cells transform into antigen-presenting cells (APCs), which then communicate with the rest of the immune system.

The immune system has difficulty recognizing cancer cells as harmful because they appear similar to normal cells. Immunotherapy works by helping the immune system to recognize cancer cells as foreign substances so it can attack them. Immunotherapy also strengthens the immune system’s response. The immune system attacks cancer cells throughout the body.

Figure 1

How immunotherapy differs

An important characteristic of immunotherapy is that it affects primarily cancer cells. Other forms of treatment are more likely to affect healthy cells as well as cancer cells. For example, chemotherapy and radiation therapy kill rapidly multiplying cells, which include cancer cells as well as healthy cells that also multiply quickly, such as blood cells. The accompanying destruction of healthy cells and tissues contributes to common side effects, such as fatigue, nausea and vomiting, and low blood counts. Immunotherapy is different because it primarily targets cancer cells, and the immune system can keep seeking out and attacking the cancer cells until they are eliminated. While it would be inaccurate to say that immunotherapy has no effect on normal tissues, there is every indication that these types of effects are less than those that occur with many non-immunologic approaches.

Immunotherapy has the potential to remain effective long after treatment ends, a feature called “memory.” This is the same characteristic that allows a traditional vaccine, such as the tetanus vaccine, to remain effective for many years.

Immunotherapy for prostate cancer

The first and currently only immunotherapy drug approved by the U.S. Food and Drug Administration (FDA) to treat prostate cancer is a therapeutic cancer vaccine. It is made specifically for the man receiving it. The patient’s own white blood cells (part of the immune system) are collected from a blood sample. These cells are exposed to a prostate cancer-associated protein that seeks to “sensitize” these normal cells. Once they recognize and target prostate cancer cells they are injected back into the patient’s body (see Figure 2). These modified white blood cells are now able to recognize and attack the cancer cells.

Immunotherapy clinical trials

Several immunotherapy treatments are currently being evaluated in clinical trials and must be found effective and safe before they are approved by the FDA. For more about clinical trials, click here.

 

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