Colorectal Cancer: New Treatments, Improved Prognosis

While colorectal cancer remains one of the most deadly cancers in the U.S., researchers are making steady progress against this disease. New drugs allow people with even the most advanced metastatic disease to live longer. Admittedly, there's no cure, and the improvements -- which can add several months to a patient's life -- may seem modest.

But for people living with advanced colorectal cancer -- and their loved ones -- small improvements make a huge difference. And experts are confident that treatment will keep getting better.

"I think the attitude has changed among doctors, especially when it comes to metastatic colorectal cancer," says Paulo M. Hoff, MD, an oncologist at the MD Andersen Cancer Center at the University of Texas in Houston. "We used to have a pessimistic view. But now we're seeing more patients with metastatic cancer responding to treatment. They are also responding well for a longer time."

"We have more tools than ever before to treat colorectal cancer," says Leonard Saltz, MD, leader of the colorectal disease management team at Memorial Sloan Kettering Cancer Center in New York. "What we're doing now is learning how to use them most effectively."

A Turning Point in Treating Colorectal Cancer

For decades, medications for colorectal cancer were limited to two drugs, 5-fluorouracil and leucovorin. But in 1996, things began to change.

• In 1996, the FDA approved Camptosar (irinotecan) for people with metastatic colorectal cancer that had recurred or spread beyond the colon. (Metastatic means that the cancer has spread to other parts of the body.)
  
  
• In 2002, the FDA approved the use of Eloxatin (oxaliplatin) in combination with 5-Fluorouracil and Leucovorin.

The new drugs improved survival to an extent. For example, one study published in the New England Journal of Medicine in 2004 found that adding Eloxatin to standard chemotherapy boosted survival among patients with advanced disease by 11%.

Advances in Targeted Therapies for Colorectal Cancer

Next, in 2004, came targeted therapies. Avastin (bevacizumab) and Erbitux (cetuximab) are monoclonal antibodies, a new generation of cancer drugs that can specifically target cancer tumors.

The problem with traditional chemotherapy is that it can't be focused. The drugs go through the body, affecting both cancerous cells and healthy cells alike. Targeted therapies affect the specific mechanisms that allow cancer cells to grow. As a result, they may have fewer side effects.

Avastin is modeled after the antibodies that naturally protect the body. It blocks the effects of a substance in the blood that helps tumors grow new blood vessels. This substance is called vascular endothelial growth factor (VEGF.) By preventing the creation of new blood vessels in the tumor, the cancer is "starved." Erbitux blocks the effects of a different growth factor called epidermal growth factor (EGF).

Studies have shown that these drugs do help. A 2004 article published in the New England Journal of Medicine found that Avastin, when combined with 5-Fluorouracil and Leucovorin and Camptosar for metastatic cancer, could increase life expectancy by about five months. Another 2004 article in the New England Journal of Medicine looked at people who were no longer responding to Camptosar. By adding Erbitux to Camptosar, the doctors were able to significantly slow down the progression of the disease, compared to using Erbitux alone for treatment.

But there are some drawbacks to these new drugs. For one, they are both only approved for people with metastatic cancer. They haven't yet been shown to work in earlier stages of the disease. And, they are still associated with side effects. In addition, Avastin seems to increase the risk of heart attacks and strokes, which makes it unsafe for some people, and prompted the FDA to request an additional warning to be added to the product labeling.