Drug That Targets Vasculature Growth Attacks Aggressive Thyroid Cancer, Mayo Clinic...

Drug That Targets Vasculature Growth Attacks Aggressive Thyroid Cancer, Mayo
Clinic Researchers Report

ORLANDO, May 18 /PRNewswire-USNewswire/ -- A medication that helps stop the
growth of new blood vessels has produced dramatic benefits for some patients
with aggressive thyroid cancer, research from Mayo Clinic indicates.

At the annual meeting of the American Society of Clinical Oncology (ASCO),
Mayo investigators report that cancer in about two-thirds of 37 patients with
aggressive differentiated thyroid cancer treated with the drug pazopanib
either stopped growing, or quickly shrank.

The patient responses seen to date are promising, the researchers say, because
all patients had fast-growing cancers that had spread to their lungs, with
half involving lymph nodes and 39 percent also involving bones.

"The benefits were striking in many patients to a degree we have not
previously seen in thyroid cancer in response to other therapies, including
the standard treatment of radioiodine," says Keith Bible, M.D., Ph.D., a
medical oncologist and researcher who led the multicenter clinical trial
funded by the National Cancer Institute. Most of the patients treated were
enrolled at the Mayo Clinic campuses in Minnesota and Florida.

Approximately one-third of patients achieved sustained and dramatic benefit
from pazopanib, while another one-third experienced stabilization of their
cancer or some tumor shrinkage. The remaining one-third of patients did not
benefit from the drug. The agent was also well tolerated by the majority of
patients, Dr. Bible adds.

What is not yet known, however, is the drug's effect on overall survival. "We
need more time to establish that definitively," says Dr. Bible. "The trial has
been going on for just over a year, and some of our patients are still
maintaining a response, while others have not been in the study long enough
for us to confirm duration of response." He notes that of the 37 original
trial participants, two have died -- one from cancer progression and another
from other causes.

The National Cancer Institute estimated that 37,340 new cases of thyroid
cancer would be diagnosed in 2008, with 1,590 deaths from the cancer. The
cancer is much more common in women; it is the seventh most common cancer in
women in the U.S. The occurrence of thyroid cancer has recently been rising.

Most thyroid cancers are of two major "differentiated" types -- papillary
thyroid cancer (the most common, accounting for 75 percent of cases) and
follicular thyroid cancer (15 percent).

Fortunately, most patients with thyroid cancer respond well to surgery and to
follow-up treatment with radioiodine; even if the cancer recurs and spreads,
the disease progresses slowly in most patients, Dr. Bible says. "Many patients
do well for a long time without the need of additional therapy," he says.
However, about 5 percent of these patients experience rapidly progressing
life-threatening disease that is insensitive to radioiodine and other
treatment approaches. "Until only recently, we have not had any effective
therapies for such patients."

Pazopanib is an experimental agent that is also being studied in advanced
kidney, ovarian and other cancers. The drug, administered in pill form,
targets proteins involved in angiogenesis, the growth of new blood vessels
that has a critical role in the growth and spread of tumors. The proteins that
pazopanib targets include vascular endothelial growth factor receptor (VEGFR),
platelet-derived growth factor receptor (PDGFR), c-kit and Ret.

Mayo investigators are also leading clinical trials to test pazopanib in two
other thyroid cancer subtypes -- medullary, which does not respond to
radioiodine, and anaplastic, the most aggressive subtype.

Dr. Bible says plans are also under way to test pazopanib in a larger,
controlled and randomized clinical trial of patients with advanced
differentiated thyroid cancer. Researchers want to more accurately assess
benefits and risks.

About Mayo Clinic
Mayo Clinic is the first and largest integrated, not-for-profit group practice
in the world. Doctors from every medical specialty work together to care for
patients, joined by common systems and a philosophy of "the needs of the
patient come first." More than 3,300 physicians, scientists and researchers
and 46,000 allied health staff work at Mayo Clinic, which has sites in
Rochester, Minn., Jacksonville, Fla., and Scottsdale/Phoenix, Ariz.
Collectively, the three locations treat more than half a million people each
year. To obtain the latest news releases from Mayo Clinic, go to
www.mayoclinic.org/news. For information about research and education, visit
www.mayo.edu. MayoClinic.com (www.mayoclinic.com) is available as a resource
for your health stories.

VIDEO ALERT: Additional audio and video resources, including excerpts from an
interview with Dr. Keith Bible describing the research, are available on the
Mayo Clinic News Blog.

SOURCE Mayo Clinic

Karl Oestreich of Mayo Clinic, +1-507-284-5005 (days), +1-507-284-2511
(evenings), newsbureau@mayo.edu