 When
64-year-old Rochelle Laurent toddled off to her GP to
check into her abdominal pain, she didn't know how important
that appointment would be. "I'm so lucky," she said tearfully.
"I was crushed when my doctor told me that I have an ovarian
tumour. Thankfully, he says that it's easily treatable
because they caught it early." Most women with ovarian
cancer aren't so lucky � although five-year survival rates
are over 95% among women whose tumours are detected early
on, only 25% of ovarian tumours are discovered soon enough.
A simple, effective screening test for ovarian cancer
could boost survival rates dramatically. According to
research published in the August 15 issue of Cancer
Research, such a test may be just around the corner.
Researchers at Johns Hopkins Kimmel
Cancer Center have identified three proteins � a truncated
form of transthyretin, apolipoprotein A1 and a fragment
of inter-trypsin inhibitor heavy chain H4 � that they
believe are significantly affected by the presence of
ovarian cancer, but not by other tumours or diseases.
"We are focusing on the markers
for which we have good biological reasoning behind their
selection, and hope to expand the panel of markers to
catch as many variations in ovarian cancer proteins
as possible," said lead researcher Daniel Chan, PhD.
The proteins' association with
ovarian cancer was discovered by testing 195 blood samples
from two groups of patients, healthy people and patients
with benign ovarian tumours. A computer program picked
out proteins that were consistently at abnormal levels
in the ovarian cancer patients.
Having controlled for differences
in patient characteristics and blood collection techniques,
the researchers were left with three proteins that tended
to be expressed abnormally in the cancer patients. They
developed a test that looked for those three biological
markers, and also for the protein CA125, which is associated
with ovarian cancer, though not strongly enough to be
used in a stand-alone test.
"Typically, only half of early
stage ovarian cancer patients have high blood levels
of a standard marker called CA125," said co-author Zhen
Zhang. "But combining CA125 with our new markers may
improve early detection capabilities."
The new four-protein test correctly
identified cancer in 17 of 23 blood samples. Not satisfied
with this, the researchers lowered the cut-off value
for elevated CA125. The new test detected 19 of 23 cancers.
In addition, it correctly identified healthy samples
94% of the time. Moreover, the test is specific for
ovarian cancer as patients with other cancers had near-normal
levels of all tested proteins.
Professor Chan said his group is
looking for further proteins to improve the accuracy
of the test, but concedes that 100% sensitivity and
specificity is an impossible dream: "The goal is to
come as close as possible to that by using this test
in combination with other available diagnostic tools."
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