Thursday 11 September 2008

Prostate Cancer

Emerging Therapies

In labs around the world, researchers are busy identifying new drugs, new regimens, and new treatment approaches that might prove beneficial to men with prostate cancer. Most of these investigational agents are being tested in men with advanced prostate cancer: Therapy options for men at this stage of disease are often not effective enough to halt progression of the disease, and men are typically affected by side effects from the disease and/or the medications that they’re taking. It’s therefore the perfect stage at which to test out new drugs because any improvement will likely be rapidly noticed and much appreciated.


The Goal of Targeted Therapies

Chemotherapy drugs can play an important role in improving the lives of men with advanced prostate cancer, but they often don’t distinguish between tumor cells and healthy cells and can kill off some normal cells along the way. So-called targeted therapies, by contrast, are drugs that are specifically designed to interfere with the way cancer cells grow, with the way cancer cells interact with each other, and/or with the way that the immune system interact with the cancer.

There are a number of different kinds of targeted therapies being investigated for prostate cancer. As of yet, none have been approved by the FDA for use in prostate cancer, but the excitement generated by some of the early studies have led many researchers to believe that it’s only a matter of time before a targeted therapy is found that can result in better outcomes overall.


Interfering With Cancer Cell Growth

All cells in the body, including cancer cells, rely on a complex communication system to know when to grow, when to divide, and when to die. This system uses specialized proteins, fats, and other substances to tell the different cells or parts of cells how to act. Over the years, cancer researchers have been studying ways to interfere with the signaling system that regulates the growth of cancer cells.

So far, interfering with cellular signaling to halt cancer cell growth hasn’t yet proven to be a very effective strategy in prostate cancer. But in the process of learning which drugs might work and why, researchers found that the strategy of adding a "targeted therapy" to other effective drugs in order to see better results than with either drug alone is an important part of cancer research. The idea is to exploit the synergy between the two drugs, or the ways in which the two drugs might work together to fight off the cancer.


Interfering With Cancer Cell Spread

As cancer cells divide and start to spread, new blood vessels sprout from the old ones to help supply the necessary nutrients to the new tumor site via a process called angiogenesis. If angiogenesis could be inhibited, researchers theorized, the new tumor cells would die and the cancer’s growth would be halted.

In 2004, the angiogenesis inhibitor bevacizumab (Avastin) was approved by the FDA for use in colorectal cancer. Since then, it has been shown to improve outcomes in women with breast cancer, and is currently being studied in a number of other cancer types, including prostate cancer. Although no other drugs currently available were designed to specifically act as an angiogenesis inhibitor, researchers have found that the drug thalidomide (Thalomid) has some anti-angiogenic properties, and is also currently being tested in men with prostate cancer.


Harnessing the Immune System to Fight Off Cancer Cells

In order for the immune system to fight off foreign invaders, it has to learn to recognize what’s normal and what’s not normal. Unfortunately, because cancer cells start out as normal healthy cells, the immune system never has a chance to learn to distinguish between the normal cell and the cancer cell.

Unlike preventive vaccines, which are designed to teach the immune system to develop a way to fight off a specific virus should it come into contact with that same virus again, therapeutic vaccines stimulate the immune system to recognize and fight certain proteins specific to cancer cells. Each of the therapeutic vaccines currently being tested in men with advanced prostate cancer works in a slightly different fashion, but all are designed to harness the immune system’s ability to fight off disease and teach it to fight off prostate cancer cells.

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