Colorectal Cancer: New Treatments, Improved Prognosis
New drugs show promise, but more research needs to be done.
Advances in Targeted Therapies for Colorectal Cancer continued...
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.
Fine-Tuning Chemotherapy for Colorectal Cancer
With more drugs to use for colorectal cancer, doctors are now trying them in new combinations and sequences.
Experts have developed a number of regimens that combine the benefits of different drugs. For some time, IFL or the "Saltz Regimen" (Irinotecan, 5-Fluorouracil and Leucovorin) was a primary treatment. But new regimens have eclipsed it, Hoff tells WebMD.
"IFL has largely been abandoned in the U.S.," says Hoff, "It's considered a little more toxic and less effective than FOLFOX (Folinic Acid, Fluorouracil, Leucovorin, and Oxaliplatin) and FOLFIRI ( Folic Acid, Leucovorin, Fluorouracil, and Irinotecan)."
In people with metastatic cancer, these regimens may be combined with Avastin or Erbitux. Many other combinations, including the use of Avastin and Erbitux at the same time, are being tested in clinical trials.
Researchers are also studying whether Avastin and Erbitux could be used in earlier stages of the disease, when the chances of actually curing the cancer are much higher. However, the results of those trials are a ways off, says Hoff.