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.