Drug Combo May Fight Prostate Cancer
Thalidomide Plus Avastin Shows Promise for Treatment of Advanced Prostate Cancer
By
Charlene Laino
WebMD Health News
Reviewed By
Brunilda Nazario, MD
Feb. 18, 2008 (San Francisco) -- A drug cocktail that starves tumors of
their blood supply shows promise for the treatment of men with advanced prostate cancer.
A combination of Avastin and thalidomide -- both of which cut off the growth
of new blood vessels that feed tumors, but in different ways -- appears to pack
a more potent punch than Avastin alone, researchers report.
Avastin was the first of a new kind of cancer therapy that works by
choking off the blood supply to a tumor, a process called anti-angiogenesis.
It's already approved for use in fighting colon and lung cancer.
Avastin blocks a chemical signal called vascular endothelial growth factor,
or VEGF. VEGF binds to certain cells to stimulate new blood vessel
formation.
Many people have heard of thalidomide. Its use in treating sickness during pregnancy in the 1960s resulted
in birth defects. The birth defects were caused because thalidomide changes the
growth and development of new blood vessels, including those in developing
babies.
But thalidomide also blocks the action of another chemical signal that spurs
the growth of new blood vessels that feed tumors. This one's called fibroblast
growth factor.
"We reasoned that combining two different anti-angiogenesis drugs that work by two different pathways to get to the
same goal would result in improved antitumor activity," says researcher
Yangmin Ning, MD, a researcher with the National Cancer Institute.
Combination Treatment for Prostate Cancer
Ning and colleagues studied 60 men with prostate cancer that had spread to
other parts of the body. They were all given an anticancer cocktail that
contained Avastin, thalidomide, and the chemotherapy drug Taxotere.
Taxotere, which is given with the steroid prednisone, is a standard treatment for men with advanced prostate cancer.
The findings were presented at the 2008 Genitourinary Cancers Symposium,
which is co-sponsored by the American Society of Clinical Oncology (ASCO) and
two other cancer care organizations.
Results showed that 90% of men improved on the drug cocktail, as measured by
a PSA drop of 50% or more.
PSA, or prostate-specific antigen, is a protein produced by cells in the
prostate. High PSA levels can signal cancer; men with a faster PSA drop after
treatment tend to have better outcomes. The National Cancer Institute says a
reduction in PSA of 50% or more after treatment is a sign that the patient is
responding to the treatment.
While the study did not directly compare the anti-angiogenesis cocktail with
other drugs, Ning says typically only about 50% of men respond to the standard
combination of Taxotere and prednisone.
Adding Avastin alone to Taxotere and prednisone raises the response rate to
60% to 70%, he tells WebMD.
"These data appear to support our hypothesis, which may lead to a novel
strategy of improving Taxotere-based treatment of advanced prostate
cancer," Ning says.
There were some serious side effects, including internal bleeding, clotting,
and perforations (holes) in the colon, mainly due to Avastin. Three men had to
drop out of the study due to Avastin-associated toxicities.
ASCO spokesman Howard M. Sandler, MD, a radiation oncologist at the
University of Michigan, says the results are promising. He notes that
results of a large clinical trial testing Avastin and Taxotere against Taxotere
alone are due out next year.
"If a benefit is shown for adding Avastin, the standard of care for
these patients will switch to Avastin plus Taxotere. This study is testing the
next avenue of approach -- adding a third agent to that doublet," Sandler
tells WebMD.
SOURCES: Genitourinary Cancers Symposium, San Francisco, Feb. 14-16, 2008. Yangmin Ning, MD, associate investigator, branch of medical oncology,
National Cancer Institute, Boston. Howard M. Sandler, MD, spokesman, Genitourinary Cancers Symposium;
department of radiation oncology, University of Michigan, Ann Arbor. Brian Rini, MD, Memorial Sloan-Kettering Cancer Institute, New York City.
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