This has opened the door for new and better ways to stop or reverse these steps. Scientists are hard at work testing and perfecting promising new approaches to cancer treatment.

Here are some of the most exciting areas of research.

Targeted approaches

While the treatment strategies in general use now (i.e., surgery, chemotherapy, and radiation) are successful in some cancers, they all have limitations. For example, they don't always kill every cancer cell, or they kill normal cells as well as cancer cells. Now, scientists are developing better ways to target therapies directly to the tumour while protecting healthy cells. Strategies include:

-- attacking the unique characteristics of the cancer cells
With a better understanding of how cancer cells grow and spread, researchers are beginning to focus in on various ways to change how they grow and spread.

-- making a tumour more susceptible to a cancer drug
Because drugs can now be better targeted to the cancer cells, stronger doses of those drugs can sometimes be given.

-- reducing side effects of cancer drugs
Newer drugs are targeted to attack only the cancer cells, without harming healthy cells. Because of this, they are less likely to cause side effects such as hair loss, nausea, and diarrhea.

Some of these targeted approaches stop the growth of existing tumours and prevent new tumours from developing. However, these treatments won't necessarily remove the cancer altogether. In the future, some cancers may be managed over long periods of time with regular drug therapies. Controlling cancer in this way would become similar to the management of other chronic diseases, such as heart disease and diabetes.

Gene therapies

Part of this new cancer treatment strategy involves changing the genes that affect how cancers grow. Scientists are testing different ways to do this. These include:

-- altering cells to boost their cancer-fighting ability
Here, scientists take cells from a patient and change them to create a healthy copy of the missing or flawed gene. They then inject these altered cells into the patient where they are better able to attack the cancer.

-- injecting a tumour with genes that will make it more susceptible to chemotherapy or other therapies

-- changing the genes of cancer cells so that the patient's own immune system will fight against them.

Immune system boosters

This immune-boosting strategy is one of the most exciting new approaches to cancer treatment. Scientists use various therapies that repair, stimulate, or enhance the immune system's natural disease-fighting ability. There are a number of agents under development that work with the immune system to help fight cancer. You may have heard of some of them:

-- interferons

These naturally occurring cancer-killing substances defend against viruses, bacteria, and other agents that cause disease.

-- interleukins

These cancer-killing substances occur naturally and can also be made in the laboratory.

-- tumor necrosis factors (TNF)

These substances target and kill cancer cells and blood vessels within the tumour.

-- monoclonal antibodies

These antibodies target specific parts of cancer cells.

Vaccines

As with vaccines for polio, hepatitis, and other diseases, the aim of a cancer vaccine is to get the body's immune system to attack foreign materials in the body. Researchers get the body to recognize this foreign material by introducing a small amount of the target material (or the antigen). To make these targets for cancer vaccines, scientists take parts of tumour cells (i.e., proteins or enzymes) that are unique to those cells and make them harmless. They then inject this vaccine into the body.

Experimental cancer vaccines that may be able to prevent or treat cancer target different parts of the immune system. Some try to induce an antibody response to prevent cancer in the first place. Others activate an arm of the immune system to kill cells that are already cancerous.

Cancer vaccines are proving promising for the following types of cancer:

-- melanoma (skin cancer)

-- colorectal cancer

-- breast cancer

-- prostate cancer

-- lymphoma.

The vaccines being tested now are injected. However, investigators are also looking at the possibility of developing a vaccine that could be swallowed, sniffed, or given in some other way.

There's still much research still to do, but if these new cancer vaccines prove successful, they could eventually become part of standard cancer therapy. They could be used, for example, with already available treatments, such as chemotherapy, in-patients who have had cancer and are at high risk of their cancer returning.

Blocking a tumour's blood supply

A tumour needs a constant supply of blood and nutrients for it to grow. Its ability to produce new blood vessels is called angiogenesis. Scientists are studying ways to cut off the tumour's growing blood supply that will essentially starve the tumour to death. They are developing a number of drugs that may block angiogenesis. These agents are called angiogenesis inhibitors or anti-angiogenesis drugs.

Hormone therapy

Some cancers are very sensitive to hormones, such as certain breast cancers and prostate cancer. Scientists are perfecting ways to give agents that suppress estrogen in women with breast cancer and other agents that block androgens in men with prostate cancer.

Killing tumours using light

Surgery has been used successfully for many years to remove cancerous tumours. However, not all cancers can be surgically removed. Even when they can be, some cancerous cells may have been missed. Researchers are experimenting with new methods that can be used along with surgery. One of the most exciting developments is the use of light.

A light-sensitive drug is given to patients before they undergo surgery. After surgery, a laser beam is directed at the tumour site where the drug has accumulated. The light triggers the drug to release chemicals that kill any of the cancer cells that were missed, without affecting any healthy cells. This technique has been used in early stages of bladder and esophageal cancers, and is now being tested in brain cancer.