Ethel B's friends say that her photograph can be found
in the dictionary next to 'pessimist.' However, the 69-year-old
opines that the term should be 'realist,' pointing out
that her not-so-cheery outlook has recently been validated.
As if having cancer wasn't enough, Ethel has also developed
life-threatening blood clots in her lung. But Ethel's
gloomy news probably wouldn't surprise researchers at
Leiden University Medical Center in the Netherlands, whose
study, published in the February 9 issue of the Journal
of the American Medical Association (JAMA), looked
at the association between cancer and venous thrombosis.
The Dutch researchers, led by Dr
Frits Rosendaal, already knew that such an association
existed but it was unclear how tumour location fit into
the picture. Also, many questions remained surrounding
the spread of the cancers, and the inherited predisposition
to genetically mucked-up versions of the blood clotting
stalwarts prothrombin and factor V Leiden — named
after the Dutch city. So in a study they grandly dubbed
Multiple Environmental and Genetic Assessment (MEGA),
the researchers set out to find cancer patients with
an increased risk of thrombosis in order to determine
the effects of these factors.
They had a big population to draw
from: 3,220 patients aged 18-70 with a first deep venous
thrombosis of the leg or a blood clot in the lungs were
identified from six anticoagulation clinics in the Netherlands
between March 1999 and May 2002. The 2,131 control participants
were made up of patients' partners.
Both groups responded to a questionnaire
designed to collect information on the participant's
risk factors for venous thrombosis. Then, three months
after the cancer patients' anticoagulation therapy had
ended, they and the controls were interviewed and a
blood sample was drawn. The blood was used for DNA analysis
of genes that encode factor V Leiden and prothrombin
20210A, which have both been linked to thrombosis.
UNLUCKY
7-FOLD
Cancer patients were seven times more likely to develop
venous thrombosis, compared to those without cancer.
And for those unfortunate enough to have blood-related
cancers — their risk of thrombosis soared 28-fold.
Lung and gastrointestinal cancers carried lower but
still significant risks.
The risk of venous thrombosis was
greatest in the months immediately following diagnosis
of a malignancy. Patients with cancers that had spread
widely throughout the body had a 20 times greater risk
of a blood clot than those whose cancers were less widely
spread.
MURDEROUS
MUTANTS
Mutation in the gene for factor V Leiden in cancer patients
increased their risk by 12-fold. Findings for the prothrombin
gene were similar.
Is it worth screening for these
mutations? The authors reckoned it's not, given that
"screening for factor V Leiden or the prothrombin 20210A
mutation and subsequent prophylactic anticoagulant therapy
with an effectivity of 80% would prevent annually 7
to 27 venous thrombotic events per 10,000 patients screened."
They concluded in their paper that screening is not
"a useful strategy."
The researchers argued in their
article that a better and more cost-effective route
might be "to consider prophylactic anticoagulant therapy
for patients with cancer who have an increased risk
to develop venous thrombosis."
JAMA Feb 9, 2005,293:715-22
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