(RxWiki News) Cancer tumors survive and grow in part because of a network of blood vessels they build. This is called angiogenesis. Scientists can't fully explain the process, but are beginning to understand its origins.
Previously, a series of experimental results published from New York and Italy showed evidence that the blood vessel growth in the brain cancer glioblastoma was cancer-based growth, rather than normal blood vessels growing to feed tumors.
Angiogenesis inhibitors such as Avastin (bevacizumab) would only be effective against normal blood vessels, and researchers believed that this explains why drugs in this class stop working after short periods of time as the cancer mutates in response.
"Ask your oncologist about angiogenesis inhibitors."
Now, Charles Eberhart, M.D., Ph.D., chief of neuropathology at the Johns Hopkins University School of Medicine, weighed in on the debate. “In general, we find no evidence in our study that these vessels contain substantial amounts of cancer cells,” he said.
It follows, then, that the mechanism of drugs preventing angiogenesis should remain an effective therapy because they work on normal blood vessels.
“My first reaction to this research was ‘How could this be true?’” says Dr. Eberhart. “Our clinical experience examining tissue from brain cancers does not support it.”
Overall, more than a hundred blood vessel samples from different tumors were tested, with less than 10 percent showing any genetic markers that could possibly signify an origin from the cancer.
If blood vessels inside tumors were being formed purely from cancerous cells, they would not be affected by the angiogenesis-inhibiting drugs, and standard chemotherapy would be just as effective.
Molecular testing could not find presence of biomarkers in significant quantities, and the 10 percent of cells that did show these markers were located on the outer portion of the blood vessel in contact with the tumor, not the inside of the blood vessel which would signify growth.
One of the components of the recent debate is the accusation that scientists have been evaluating samples of cells without regard for origin, which as described above, alters the interpretation.
The team from Johns Hopkins cites improper laboratory technique as an explanation for the evidence produced by the Italy-New York team of scientists that glioblastoma angiogenesis is cancer related.
First approved by the FDA in 2004, Avastin (bevacizumab) has come into controversy several times, most recently from the announcement by the manufacturer Genentech in February that counterfeit Avastin had been found on the market.
With a cost of $40,000 - $200,000 per year depending on dosage, Avastin currently vies for the title of most expensive pharmaceutical treatment; the majority of national health services and insurance companies deny claims for the drug.
Avastin has FDA approval for use in patients with colorectal, lung, kidney and brain cancers. Approval for use in breast cancer was revoked in 2010.
Results were published in the online journal Oncotarget.
Funding for the study was provided by the National Institutes of Health.