Colorectal Cancer: New Treatments, Improved Prognosis
New drugs show promise, but more research needs to be done.
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