14 DAY TRIAL // Recent studies have shown that cancer medicine aimed at inhibiting the vascular endothelial growth factor (VGEF) protein actually promotes tumor growth, by making the blood vessels cancerous cells build stronger and almost normal. Seeing how the tumor needs blood to feed itself, doctors thought that cutting their blood supplies would kill them. But, apparently, inhibiting VGEF is not the way to do it, as, in some cases, further investigations showed that tumors actually progressed.
"We've discovered that when anti-angiogenesis drugs are used to lower the level of VEGF within a tumor, it's not so much a reduction in the endothelial cells and losing blood vessels as it is an activation of the tumor blood vessels supporting cells. This enables vessels to mature, providing a conduit for better drug delivery to the tumor. While the tumors initially get larger, they are significantly more sensitive to chemotherapeutic drugs," explained David Cheresh, Ph.D., professor and vice chair of pathology at the UC San Diego School of Medicine and the Moores UCSD Cancer Center.
On the "bright" side, larger tumors mean that they are more susceptible to the effects of chemotherapy, which means that, clinically, drugs such as Avastin should only be used together with chemo. "It means that chemotherapy could be timed appropriately. We could first stabilize the blood vessels, and then come in with chemotherapy drugs that are able to treat the cancer," said Cheresh.
"It appears that the drugs, in shutting down VEGF activity, are actively maturing blood vessels, causing them to become stable and more normal, as opposed to reducing blood vessels. When you take away the VEGF, you 'take the foot off of the brake'."
Oncologists say that certain cancer therapies will have to be revised in light of the new find, so as to maximize their efficiency. The good news is that the new combo treatment will most likely work on all tumor types, as VGEF is not specific to a certain kind of tumor.