SAN FRANCISCO--Recent research assessing the skills of todays
clinicians in interpreting genetic tests for colon cancer (FAP and
HNPCC) finds they fall woefully short, Francis M. Giardiello, MD,
associate professor of medicine and gastroenterology, Johns Hopkins
University School of Medicine, said at the American Cancer Society
Second National Conference on Cancer Genetics.
Clinicians need to know how to interpret such tests accurately and
need to provide thorough and painstaking counseling to families
facing fatal genetic disease, Dr. Giardiello said.
In one study of 177 patients under the care of gastroenterologists
and oncolo-gists, "there was a lack of pretest counseling as
well as a high rate of incorrect test interpretations," Dr.
Giardiello said. "This is a real problem for the families as
well as a legal landmine for clinicians."
The study of patients from 125 families at risk for familial
adenomatosis polyposis (FAP) showed that the clinicians provided
correct test interpretation only 68% of the time (Giardiello FM et
al: N Engl J Med 336:823-827, 1997). More than 30% of
the time, the doctors told the patients that tests were negative when
they were, in fact, inconclusive. "As a result, the patients
would not have got increased screening--and 10 years later could
develop incurable colorectal cancer," Dr. Giardiello said.
Just as woefully, only 19% of doctors in the study offered their
patients pretest genetic counseling and only 17% obtained informed
consent before testing, he said.
Ideally, genetic counseling should begin before the test--and should
be done by a professional genetic counselor, face-to-face with the
patient, Dr. Giardiello said. The counseling session should provide
the clinician with data about the patients pedigree and allow
the patient to begin to comprehend the risks associated with full
disclosure of test results.
Delving into the patients understanding of family relationships
and life experience can help both the counselor and patient grapple
with the issues that may arise with positive test results, Dr.
Giardiello said. These can include the possibility of falling victim
to a fatal disease, experiencing genetic discrimination, and having
to tell their children of the test results, he added.
"The counseling session should also provide education for the
patient. The counselor should talk about the clinical management of
the disease, if it develops, and steps to be taken for increased
screening if the test is positive," he said. "The important
last step is to get written informed consent."
Ironically, disclosing the results of these genetic tests can have
both positive and negative emotional impact on a family, studies
reveal. If the test is positive, patients may be devastated by the
fact that they have a "bad gene," may worry about their
children, and may fear eventual surgery and a changed lifestyle. They
may feel stigmatized by their family and friends, and find that the
disease--or their anxiety about it--interferes with work or school.
On the other hand, a positive result removes doubt about whether or
not the patient carries the gene. Both doctor and patient can set
their sights on frequent screening to detect early polyps.
"People who do undergo the test and get positive results do tend
to show increased compliance with frequent surveillance. And if the
doctor and patient know early enough about the chance of cancer,
theres a greater choice of surgical and medical options,"
Dr. Giardiello said.
A negative test result, of course, tends to relieve most patients.
Their children will be unaffected, they will have fewer medical
costs, and the family will be insurable. But some patients may
experience "survivor guilt" when other members of their
family get positive test results, he said.
Along with its emotional impact, the cost of genetic testing for
colon cancer--at $200 to $2,600--is high, Dr. Giardiello
acknowledged. But when measured against a lifetime of conventional
screening for at-risk individuals, beginning at age 12, its
much cheaper--in fact, at least, $600 cheaper over a lifetime--a
study by Dr. Giardiello and colleagues reveals.