SAN DIEGO - The chances of a patient developing multiple primary melanomas over a lifetime is a real phenomenon, with an incidence ranging from 2% to 8% among patients who have had a first melanoma, or an average of about 5%.
Of patients who develop additional melanomas, about 80% develop one in addition to the original, 15% develop two, and the remainder develop three or more. "In my practice I have about four people I follow who have had five or six primary melanomas," said Dr. Burrows, who has practiced dermatology for nearly 40 years and is currently with the division of dermatology at Scripps Clinic Rancho Bernardo in San Diego. "We've become the primary care physicians for patients with melanoma."
He went on to note that the risk of multiple primary melanomas is twofold higher among men, and that the majority of subsequent primary melanomas (70%) occur on a different anatomical site, while 30% occur on the same site.
"They have the same distribution as melanomas in general," he said.
The majority of subsequent primary melanomas occur after 2 months, while 30% occur within 2 months or less.
Depth of invasion is similar to national statistics for all primary melanomas. "But the second primary melanoma tends to be thinner than the first one, which makes sense," Dr. Burrows commented. "After the first primary melanoma we raise our index of suspicion on lesions that are irregular. In addition, the patient has a significant level of worry."
Recognized risk factors for multiple melanomas include presence of atypical/dysplastic nevi, family history, and early age of onset.
According to a retrospective review of 1,258 melanoma patients treated at the Scripps Clinic between 1990 and 2000, 149 (12%) developed multiple primary lesions, which is more than double the national incidence. "This could be due to one of two things," Dr. Burrows said. "One is the criteria that are used in making the diagnosis of melanoma in situ. I wonder if we [at Scripps] diagnose melanoma in situ more often, as opposed to others who might sign it out as atypical melanocytic hyperplasia or another worrisome diagnosis."
The other possibility is that incidence of melanoma is rising. "We know that we are making the diagnosis of primary melanomas at a younger age than we did 20 years ago," Dr. Burrows said.
In the Scripps series, 75% of patients had two primary melanomas, 15% had three, and the remainder had four or more. The average age at initial primary melanoma diagnosis was 64 among men and 56 among women.
Nearly half of the patients (49%) developed subsequent melanomas less than 3 years after their initial primary melanoma diagnoses.
At this point, Dr. Burrows does not recommend testing for the CDKN2A and CDK4 gene mutations in most patients. "It's not a good screening tool for the general population or fair-skinned population with multiple nevi, but it has potential use in screening patients with a family history of melanoma," he said.
"You want to know if they have a 75%-100% risk of developing melanoma. But in my opinion, this test is not helpful in people who have had one primary melanoma. It doesn't pick out the people at risk of getting a second primary melanoma."
As for managing patients with multiple melanomas, a full skin exam during initial workup and follow-up intervals is essential, he said. "Follow-up should be lifelong."
Dr. Burrows had no conflicts to disclose.
(Image above is of Dr. William M. Burrows/Photo credit: Doug Brunk)