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
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