New Drug Improves Colon Cancer Survival
Avastin Starves Tumors by Cutting Off Blood Supply
Jan. 3, 2003 -- A new kind of cancer treatment makes chemotherapy work better in people with advanced colon cancer.
The treatment is Avastin -- formerly called anti-VEGF -- the first of a new kind of cancer therapies. Conventional chemotherapy simply kills fast-growing cells -- including cancer cells and normal cells. Avastin keeps tumors from growing new blood vessels. This starves the tumor and slows or even stops its growth.
If an early cancer wasn't able to grow a new blood supply, it wouldn't get much bigger than a pinhead. But the new treatment is first being tested in people with advanced, spreading cancers. UCLA researcher Fairooz Kabbinavar, MD, studied the drug in patients with metastatic colon cancer.
"This study could give us a less toxic and a more effective weapon in our growing arsenal of cancer therapies," Kabbinavar says in a news release.
All 104 patients in the study received standard chemotherapy with fluorouracil and leucovorin. Two thirds of them also got high- or low-dose Avastin. Those who got Avastin -- particularly those who got the lower dose -- did much better than those treated with chemotherapy alone.
"The patients who got Avastin and chemotherapy did better in all the parameters we use to measure efficacy," Kabbinavar said.
The lower dose of Avastin kept cancer from progressing for nine months, compared with 5 months for patients on chemo alone. Low-dose Avastin patients also were more than twice as likely to respond to chemotherapy. Even though many of the chemo-alone patients got Avastin after the initial study period, those who first got the drug had significantly longer overall survival (21.5 months vs. 16.1 months).
It's not clear why the lower dose works better. Kabbinavar and colleagues suggest that the higher dose collapsed the tumors but did not kill them. The lower dose shrank the tumors but left their blood vessels working well enough to let in a lethal dose of chemo.
Avastin can have very serious side effects. One treated patient died from a blood clot; several other patients also had blood-clotting events. Other safety concerns included high blood pressure and nosebleed.
A larger Avastin clinical trial with 1,000 patients already is finished. Results are expected sometime next year. These findings are expected to show whether Avastin is ready for more widespread use.
Other studies are studying Avastin as a possible treatment for cancers of the lung, breast, prostate, and kidney. One other question left unanswered is what effect Avastin would have on less advanced tumors.