What's New in Colorectal Cancer Research and Treatment?

Detailed Guide: Colon and Rectum Cancer

Research is always under way in the area of colorectal cancer. Scientists are looking for causes and ways to prevent colorectal cancer as well as ways to improve treatments.

Chemoprevention: Chemoprevention is the use of natural or man-made chemicals to lower a person's risk of developing cancer. Researchers are testing whether fiber supplements, minerals (such as calcium), and vitamins (such as vitamin D), can lower colorectal cancer risk. Some studies have found that people who take multivitamins containing folic acid (also known as folate) have a lower colorectal cancer risk than people who do not. Recent studies have found that people who took vitamin D supplements had a reduced rate of colorectal cancer. Increasing calcium intake by using calcium supplements or eating extra amounts of low-fat dairy products may reduce formation of colorectal adenomatous polyps.

Although taking aspirin or some other non-steroidal anti-inflammatory drugs (NSAIDs) is associated with a lower risk of colorectal cancer, these drugs can cause stomach ulcers and other side effects. For this reason, taking NSAIDs specifically for this purpose is not recommended for people at average colorectal cancer risk. You should consult with your doctor before beginning regular use of aspirin or another NSAID.

NSAIDs, such as sulindac and celecoxib (Celebrex), have been shown to reduce formation of adenomatous polyps in people with familial adenomatous polyposis (FAP). The FDA has recently approved celecoxib for reducing polyp formation in people with FAP. However, recent celecoxib data are now being evaluated for a potential increased heart risk.

Studies indicate that a diet high in fruits and vegetables may lower colorectal cancer risk, as well as the risk of several other diseases. This hasn't been completely proven by all studies. But it is important that you eat enough servings -- at least 5 a day!

Most experts recommend that people not take large doses of vitamins, minerals, or other agents unless they are part of a study or are under the advice and care of a doctor.

Genetics: Scientists are learning more about some of the inherited and acquired changes in DNA that cause cells of the colon and rectum to become cancerous. Recent discoveries of inherited genes that increase a person's risk of developing colorectal cancer are already being used in genetic tests to inform people most at risk.

Advances in understanding how these genes work are expected to eventually lead to new drugs and gene therapies to correct these gene problems. Early phases of gene therapy trials are already in progress. Researchers have developed ways to package DNA of normal p53 genes into a virus designed in the laboratory. Most colorectal cancer cells have defects of this tumor suppressor gene that contribute to their abnormal growth and spread. Studies are under way to see whether these designer viruses containing normal p53 genes can infect colorectal cancer cells and either stop their growth or cause them to "self-destruct."

Earlier detection: Studies continue to evaluate the effectiveness of current colorectal cancer screening methods and evaluate new approaches to informing the public about the importance of taking advantage of these methods. Less than half of Americans age 50 or older have any colorectal cancer screening at all. If everyone were tested as recommended, tens of thousands of lives could be saved each year. The American Cancer Society and other public health organizations are working to increase awareness of colorectal cancer screening among the general public and health care professionals. Meanwhile, new imaging and laboratory tests are also being developed and tested.

Virtual colonoscopy (also known as CT colonography) is a special type of CT scan that can find colorectal polyps and cancers at least as accurately as a barium enema. This test is described in more detail in the section, "Can Colorectal Polyps and Cancer Be Found Early?" Although virtual colonoscopy is currently not included among the tests recommended by American Cancer Society for early detection of colorectal cancer, the Society is carefully following progress in this area as technology improves and more results become available about its accuracy.

Immunotherapy: Experimental treatments that boost the patient's immune reaction to fight colorectal cancer more effectively are being tested in clinical trials. Some treatments use drugs like interferons and interleukins that boost the immune system in general.

In active immunotherapy, the patient is given a vaccine that might cause the immune system to recognize some of the abnormal chemicals in colorectal cancer cells and kill these cells. For example, the K-ras oncogene product is altered in many colorectal cancers and researchers are testing ways to help the patient's immune system attack cells with an altered ras protein. Researchers are also testing vaccines to direct a patient's immune system to attack colorectal cancer cells that produce carcinoembryonic antigen (CEA). There are also studies where patients' tumor cells are used to produce a vaccine. The vaccine is used for adjuvant therapy in the hope of preventing recurrence.

Passive immunotherapy uses antibodies made in the laboratory and then injected into patients to seek out colorectal cancer cells that contain abnormal ras protein or other abnormal or overproduced proteins like carcinoembryonic antigen (CEA) or the HER-2 oncogene product. Toxins or radioactive atoms can be attached to these antibodies, so that the cell-killing chemicals or radiation is targeted specifically to the cancer cells and do not attack the healthy cells of the body. Two antibodies, cetuximab (Erbitux) and bevacizumab (Avastin), are discussed below.

Tumor growth factors: Researchers have discovered naturally occurring substances in the body that promote cell growth. These hormone-like substances are called growth factors. Growth factors activate cells by attaching to growth factor receptors, which are present on the outer surface of the cells. Some cancer cells grow especially fast because they contain more growth factor receptors than normal cells do. One of the growth factors that has been linked to colorectal cancers is called epidermal growth factor (EGF).

New drugs like cetuximab (Erbitux) and panitumumab (Vectibix) that specifically kill cancer cells by attacking EGF receptors have proven effective and are now being used. More are being developed.

Another growth factor, known as vascular endothelial growth factor (VEGF), helps tumors develop new blood vessels to get nutrients. Several drugs are now in development to try to block VEGF in order to cut off the tumor’s blood supply. These drugs are known as antiangiogenesis drugs.

One such drug, bevacizumab (Avastin), is a monoclonal antibody that attacks VEGF. This has proven effective also and is now being used to treat colorectal cancer. Other drugs that act against blood vessels are being developed and tested.

Chemotherapy: Many clinical trials are testing new chemotherapy drugs or drugs that are now used against other cancers (such as cisplatin or gemcitabine). Other studies are looking at ways to combine drugs already known to be active against colorectal cancer, such as irinotecan or oxaliplatin, to improve their effectiveness. Newer studies are adding cetuximab or bevacizumab to chemotherapy as adjuvant therapy. Still other studies are testing the best ways to combine chemotherapy with radiation therapy and/or immunotherapy.

Revised: 02/22/2007