Genetic Tests Scan for Potential Cancer, Other Diseases

PALM BEACH, Fla. -- As unsettling as it sounds, a portion of one's risk for developing disease is set at the moment of conception, when two disparate sets of DNA merge. A predisposition for disease does not always translate into actual illness, and environmental factors can influence disease development, for better or worse.

However, knowing one's genetic predisposition for certain diseases -- including cancer of the breast, prostate, skin, ovaries and pancreas -- can be used to keep a possibility from becoming a life-threatening reality.

Dr. Elisabeth McKeen, an oncologist with the Palm Beach Cancer Institute at Good Samaritan Medical Center, uses genetic testing to screen select patients for their risk of developing these types of cancer. A test for colorectal cancer is one of the newer tests. As much as 15 percent to 20 percent of colon cancer is hereditary, McKeen said.

When she began doing genetic screening, in 1997, McKeen performed fewer than 50 tests. This year, the Institute will do about 300.

"Insurance is becoming more and more willing to pay for them, so that's the big progress," McKeen said. "Because with insurance covering them, then more people have the testing available."

The tests can cost from several hundred dollars to a few thousand, she said. "When you test the first family member, it's usually a couple thousand. If you find a mutation, then the other family members can be tested for $400."

McKeen said there is no charge for tests still under investigation. Other agencies can subsidize some tests for people without insurance. This year, the Susan G. Komen Breast Cancer Foundation's South Florida affiliate gave PBCI a grant of $40,000 to pay for genetic screening for breast cancer susceptibility.

A recently developed test screens for a predisposition for melanoma and pancreatic cancer. "When you have a gene that's not functioning, it affects many different organs," said Catherine Kirvin, risk-screening counselor at PBCI.

Family history is the predominant factor in determining whether genetic testing is recommended, McKeen said. While women with the BRCA1 gene mutation (including some Ashkenazi Jews) may have as much as an 85 percent risk of developing breast cancer and a 44 percent risk of developing ovarian cancer across their lifetime, most women have a smaller risk (12 percent and 1 percent, respectively), according to McKeen.

Those in the latter group would not be candidates for genetic screening for breast cancer unless there is strong evidence that breast cancer has impacted more than two generations. Similarly, McKeen does not advise patients to undergo multiple genetic tests.

Some family members may be reluctant to get a test -- and discover they have a higher-than-average predisposition for a disease. Members who have had genetic testing, though, can suggest it, without indicating whether their own test was positive or negative, McKeen said.

As part of a Duke University-led study, McKeen recently began asking some of her breast cancer genetic screening patients to donate a blood sample when they return for a follow-up visit. Duke will analyze the blood samples collected from this and other clinical partners to determine the role other genes play in the expression of BRCA1 and BRCA2 mutations. Scientist want to know whether these cofactor genes impact the timing of the onset of breast cancer. Another issue is whether cofactor genes trigger the development of breast cancer in people with a strong family history of the disease, but do not have BRCA mutations.

The study could lead to treatments that suppress BRCA mutations, McKeen said.

Impact of test development

Once genetic testing confirms an individual is more susceptible to developing a disease, his or her doctor can monitor the person's health via scanning to catch tumors in the earliest stages, when they are often most successfully treated.

And, recent studies indicate that preventive surgery such as prophylactic mastectomy (the removal of breast tissue with reconstruction without lymph node removal) and the removal of the ovaries can cut the occurrence or reoccurrence rates of these cancers drastically, McKeen said.

Prophylactic mastectomy can reduce the reoccurrence of breast cancer by more than 98 percent, McKeen said. Removal of the ovaries decreases the risk of ovarian cancer and primary peritoneal (cancer of the abdominal lining) by 95 percent, while also decreasing the risk of breast cancer, McKeen said.

"So, not only do we identify the people but now we can really prevent the cancers by having women have their ovaries out and they can elect to have prophylactic mastectomies or they can be watched," McKeen said.

The completion in 2003 of the Human Genome project was the impetus for the surge in genetic testing.

Medical researchers have created more than 1,200 genetic tests, many of which are for less common diseases such as Huntington's disease, muscular dystrophy and cystic fibrosis, according to Dr.

Geoffrey Ginsburg, director of the Center for Genomic Medicine at the Duke Institute for Genome Sciences & Policy.

Scientists are broadening the scope of their research and are now investigating genetic tests and pharmaceutical treatments for diseases that impact large segments of the population, including cardiovascular disease.

Genetic screening will play an increasingly larger role in treatments for disease in the future, according to Ginsburg.

"If you look at the clinical research papers and scientific publications today, hardly a week or maybe even a day goes by when we are not seeing more information coming out that allows us to have a better understanding of disease and disease mechanism -- as well as these abilities to detect disease before it has a chance to clinically manifest," Ginsburg said.

David Rogers writes for the Palm Beach Daily News. E-mail: drogers@pbdailynews.com Editor Notes: