The Effectiveness Of Avastin
New studies show that blood vessels that nourish tumors in the brain are not formed by cancer cells, as scientists previously thought. These discoveries, made by scientists at Johns Hopkins University School of Medicine, dispute the effectiveness of current treatments against cancer, such as Avastin (Bevacizumab).
Charles Eberhart, MD, Ph.D., chief of neuropathology at the Johns Hopkins University School of Medicine, said that the studies done by his team do not clearly show that the tumor blood vessels should be composed of cancer cells. He added that purpose of the study was not to call into question whether brain tumors express markers for blood vessels, but to what extent this fact occurs.
For the tumor to grow, it needs blood supply, which develops as a result of growth factors released by tumor. Cancer cells release various growth factors such as VEGF, vascular endothelial growth factor that stimulates angiogenesis. Based on this mechanism, scientists have developed various therapies in metastatic cancers. Bevacizumab is a monoclonal antibody that inhibits angiogenesis as it acts as an inhibitor of VEGF function. Bevacizumab was approved by the FDA for the treatment of colorectal cancer, kidney, brain and lung cancer. Bevacizumab was also approved in the treatment of breast cancer in 2010 but it was withdrawn because it was not safe and it did not prolong life in patients with breast cancer.
More recent studies conducted by scientists in Italy and the Memorial Sloan Kettering Cancer Center in New York, actually showed that blood vessels in brain tumors are not made up of cancer cells but stem cells. These findings may explain why tumors respond to Bevacizumab but only for a short period. Also, researchers found that those cells that form blood vessels are resistant to treatment. Therefore, as long as tumors have blood supply and are nourished, it is difficult to shrink those tumors. Therefore, studies have focused on the application of targeted treatment to combat cancer, such as angiogenesis inhibition.
Eberhart and his colleagues have analyzed over 100 samples of patients with brain cancer at the Dana Farber Cancer Institute and Johns Hopkins, and studied the molecular features of blood vessels. They looked in particular two important cancer markers, EGFR and IDH1. They also have looked for another marker, CD34, in order to differentiate vascular cells from the rest of cells. Researchers found that only 10% of tumor samples expressed the looking markers, EGFR and IDH1. Furthermore, in rare forms of tumors, only a few cells had those markers.