May Help Predict
NEW YORK (Reuters Health) - An experimental test may help doctors
quickly determine whether a particular regimen of chemotherapy
is working, saving crucial time if another treatment approach
is warranted, preliminary research suggests.
Cancer patients usually undergo four or five courses of chemotherapy
before physicians can tell whether the treatment is having an effect,
said Dr. Neil Steinmetz, medical director of the Theseus Imaging
division of North American Scientific, Inc., the company that is
developing the new test. By that time, the tumor may have grown
so large that it is too late to switch to another chemotherapy regimen
or the patient may be so weakened by the treatment that trying another
approach is not immediately feasible, he said.
"That's a central dilemma of modern oncology," Steinmetz told
Reuters Health. "We treat a lot of patients and we don't know
going in if the treatment will work."
But the new test, known as Apomate, can predict whether chemotherapy
is working in some cancers after just one dose, according to findings
released Monday at the annual meeting of the American Association
for Cancer Research in San Francisco, California.
The test works by measuring changes that occur on the surface
of cancer cells as they are dying, Steinmetz explained. As the
cells die, a component of the cell membrane called phosphatidylserine
(PS) migrates to the membrane's outer surface. With Apomate, patients
are injected with a solution that contains both a human protein
known as annexin V, which binds to PS, and a radioactive tracer
that releases a signal that can be viewed outside the body with
an imaging device. The stronger the signals, the greater the cancer
cell death, he noted.
Steinmetz reported on a trial involving 15 Belgian patients
with inoperable lung cancer, breast cancer or lymphoma who were
given the Apomate test both before and after their first dose
of chemotherapy and then followed for up to a year. Results showed
that all seven patients who had a positive result on Apomate following
their first course of chemotherapy responded either partially
or completely to the entire course of treatment. On the other
hand, six of eight patients who had a negative result failed to
respond to treatment and either their disease progressed or they
The test was most accurate for the 10 patients with lung cancer.
"The key observation is that in the lung cancer cases, none of
the patients who showed no cell-death activity after the first
dose of chemotherapy responded to (continuing) chemotherapy,"
The test may need to be refined in different ways for different
cancers, he said. "We think it could certainly work for many if
not all cancers," he added.
Studies of Apomate are currently under way in the United States,
according to Steinmetz, and the test could be available within
the next couple of years.
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