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Conquer Cancer Health News |
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Hazards and Promise Cancer Blocking Drugs Are a Mixed Bag
Daniel Q. Haney, The Associated Press
NEW ORLEANS - Drugs designed to
stop tumors by cutting off their blood supply
have shown modest benefit in tests against three
kinds of cancer, but have also raised concerns
about possible dangerous side effects.
Angiogenesis inhibitors, as these drugs are called, are
among the most closely watched new developments in
cancer research. In animal studies, they sometimes
dramatically reverse cancer, and hopes are high they will
do something similar in people.
Several reports on mid-size studies of these medicines
were reported at this week's annual cancer conference
sponsored by the American Society of Clinical Oncology.
Together, experts say, these studies offer proof that the
concept is sound: Attacking tumors' ability to sprout
blood vessels clearly inhibits cancer growth, even in
terminally ill patients who have tried all of the standard
cancer drugs.
However, these studies also show that these drugs can
have a variety of unwanted side effects, some of which are
fatal.
Pinhead-Sized Cancers
"These are drugs in every sense of the word," said Dr.
George Sledge of Indiana University. "They have activity,
and they have toxicity."
On Tuesday, doctors reported studies on drugs
developed by Genentech and Sugen that are designed to
block tumors' use of vascular endothelial growth factor,
or VEGF. This substance is a key fuel that allows the
cancer to grow new blood vessels and repair old ones.
Without a new blood supply, cancers never get bigger
than a pinhead.
As is usual at this stage of testing, the drugs were given
only to people with spreading, incurable tumors,
sometimes alone, sometimes in combination with standard
chemotherapy medicines.
Doctors say that while no one was clearly cured, the
anti-VEGF compounds did seem to slow the tumors'
spread, at least for a few months.
"We have three common solid tumors - breast, colon
and lung cancer - and this drug shows some evidence of
clinical benefit in all three, the most common cancers we
deal with. That's the real significance," said Dr. Russell
DeVore of Vanderbilt University, referring to new results
with the Genentech drug.
Unexpected Side Effect
However, DeVore's study, conducted on 99 terminally ill
lung cancer patients, also shows the drugs' potential
hazards. Six patients developed sudden, catastrophic
bleeding in their tumors, killing four of them.
"We were taken by surprise. This was not an expected
side effect," DeVore said.
However, Dr. Nicholas J. Vogelzang of the University
of Chicago called this bleeding "very exciting," despite its
unfortunate consequences, since it suggests the treatment
truly does appear to disrupt the tumor's ability to maintain
a blood supply.
Other dangerous side effects of anti-VEGF treatment
include high blood pressure and blood clots.
Dr. Lee Rosen of the University of California at Los
Angeles tested Sugen's anti-VEGF drug, code-named
SU5416, in combination with standard chemotherapy on
28 people with advanced colon cancer. The combination
stopped cancer growth for an average of 9+ months,
compared with six months for the usual therapy.
Of the 28, "25 are still alive, some as long as a year so
far, and they are all doing very, very well," Rosen said.
Although the study is small, "the data are very interesting
and very promising. This really validates the target. By
regulating VEGF, we seem to be doing something."
Doctors were pleasantly surprised in these studies to
see evidence that the anti-VEGF drugs seem to make
tumors shrink. In theory, they might have halted cancer's
spread while doing nothing to make them go away.
The Next Phase
The data from these studies are promising enough for
Sugen and Genentech to begin large studies that will enroll
several hundred cancer patients in an attempt to prove
that the two drugs actually lengthen patients' lives.
"I continue to feel this is an enormously interesting way
to treat patients with cancer," said Dr. Susan Hellman,
Genentech's development chief. "Now we need to move
into the next phase and see how much we will help
patients and what the risks will be."
Much of the enthusiasm for blocking blood vessels
came from optimistic coverage of the development of the
drugs endostatin and angiostatin by Harvard's Dr. Judah
Folkman, the field's pioneer.
Endostatin is in early testing at three hospitals, and
participating doctors have been silent about the effects so
far. At the meeting Monday, Folkman said he is "very
pleased" with the results in Boston.
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