Understanding the benefits of p16 testing for high-risk familial melanoma patients

January 1, 2008

P16-mutation carriers are at extremely high risk for developing melanoma. Many high-risk melanoma clinics worldwide are reporting genetic test results, and clinical testing also is increasing in the United States. There are currently no guidelines regulating genetic testing in the United States, but melanoma genetics experts are working to develop meaningful guidelines that will, hopefully, be published in early 2008.

Key Points

P16-mutation carriers are extremely high-risk, says Sancy Leachman, M.D., Ph.D., associate professor of dermatology and director of the Melanoma and Cutaneous Oncology Program at the Huntsman Cancer Institute at the University of Utah.

"Dermatologists are on the front lines of preventing melanoma," she says. "Key factors in evaluating whether patients should be tested or not include considering the pros and cons of testing, and then learning about hereditary melanoma risk factors, proper identification of testing candidates, as well as following a testing protocol."

"Patients with the highest risk are those with a family history," she says, noting that clinical genetic testing is available.

There are currently no guidelines regulating genetic testing in the United States, but melanoma genetics experts are working to develop meaningful guidelines that will, hopefully, be published in early 2008.

Important risk factors for the development of melanoma include family history of melanoma and patients with previous primary melanoma or multiple nevi/atypical nevi. Other risk factors include red hair, a history of blistering sunburn, freckling, blue eyes and skin type I.

Dr. Leachman says that hereditary status cannot be detected by clinical examination.

"Although some families that carry a p16 mutation have atypical mole syndrome (AMS), not every family, nor every member of a particular family, have AMS. In addition, not all NON-p16 mutation-carrying families demonstrate AMS. Finally, some patients (and families) with AMS do not demonstrate increased incidence of melanoma," Dr. Leachman tells Dermatology Times.

Pros and cons of testing

There is some debate whether p-16 testing helps patients.

Opponents of p16 genetic testing purport that there is no patient benefit unless medical management significantly changes. In addition, they argue that because the cost of testing is high and no targeted intervention is available, patients should not be told about elevated risk until values are better defined.

"For the pro side of the debate, knowledge is power, and most patients do value the medical information. The knowledge frequently empowers lifestyle choices because the objective proof of risk is compelling," Dr. Leachman says.

"Other cancer syndromes have implemented genetic testing successfully, and the literature supports no real adverse effect, " she says.

Further, testing stresses patient responsibility for healthcare. A study at the University of Utah showed that patients value the genetic testing option.

Candidate selection

Identification of testing candidates is an individualized process.

"When considering patient selection, use the 'red flag,' three elements test: Three melanomas in family; three primaries; or three cancer combinations (of melanoma & pancreatic cancer)," Dr. Leachman says.

"Be sure to confirm cancer cases and test affected members first. In equivocal cases, use good judgment."

Protocol

Testing is performed at clinical genetic laboratories that offer p16 genetic testing. Current laboratories include GeneDX(United States), Institute Gustave-Roussy(France), Myriad Genetic Laboratories (United States) and Yale University School of Medicine (United States).

"After a dermatologist identifies high-risk patients, they should typically refer to a cancer genetics center," Dr. Leachman says.

"At the center, informed consent and pre- and post-test genetic counseling will be done. This includes family history assessment and verification of cancers, education, risk assessment and management recommendations.

"In addition, they will help patients with the emotional implications - family dynamics, guilt, etc., as well as informed consent, including issues dealing with the limits, benefits, possible results, risks of test and genetic discrimination," she says.