Melanoma rates continue to rise, especially thin lesions which represents the largest group of fatalities. Gene expression profile tests can help diagnose or predict melanoma and are easy to use. But many dermatologists do not follow recommended treatment guidelines, which indicates a need to either educate practitioners or rethink the guidelines.
The incidence of melanoma continues to rise, despite valiant efforts.
“The lifetime risk of an American developing invasive melanoma (ICD-10 C43.9) is about 1 chance in 50,” says Darrell Rigel, M.D., a clinical professor of dermatology at New York University. “And should that rate of increase continue over the next few years, the cancer will affect 1 in 40 Americans.”
Dr. Darrell RigelWhen including melanoma in situ (ICD-10 D03.9) in the calculations, an American has a lifetime risk of roughly 1 in 24.
“Melanoma is a serious public health problem, with rates rising in both men and women,” says Dr. Rigel, who presented on melanoma at the 2017 Winter Clinical Dermatology Conference in Hawaii.
The highest rate of increase for melanoma is in people over the age of 50.
“This is probably due to excessive sun exposure, for which they are unable to undo all the skin damage,” says Dr. Rigel, in a post-presentation interview with Dermatology Times.
Sun protection is the most single important action a person can take to minimize skin damage.
There is also a difference between primary prevention and secondary prevention.
“Primary prevention basically protects the person from the sun by wearing sunscreen,” Dr. Rigel says. “This affects the incidence.”
Secondary prevention entails a patient visiting a dermatologist after noticing a suspicious skin spot.
“This is early detection and impacts mortality,” Dr. Rigel says.
As to which is more important – primary prevention or secondary prevention – Dr. Rigel tends to err on the side of secondary prevention.
“It is hard to change a person’s behaviors, but you can assess a person’s skin spot,” he says.
The number of thin lesions is growing faster than the number of thick lesions.
“Today, about 75% of cases of melanoma are being diagnosed with lesions less than 1 mm in thickness,” Dr. Rigel says.
Because patients with thin lesions now represent the largest group that dies from melanoma, “it is particularly important to detect melanoma as early as possible,” Dr. Rigel says.
Several published papers over the last year conclude that melanoma itself can have its prognosis determined, even on thinner lesions.
Gene expression profiling can also help diagnose or predict melanoma. For example, myPath (Myriad Genetics Inc.) is a genetic test that profiles 23 genes to diagnosis whether a lesion is melanoma or not.
Similarly, DecisionDx (Castle Biosciences Inc.) is a 31-gene expression profile test to assess prognosis.
“The test is easy to use,” Dr. Rigel says. “You can actually obtain tissue from the laboratory instead of ordering a second biopsy.”
However, in reality, “wo specific genes may be predictive of melanoma,” Dr. Rigel says.
Dr. Rigel was co-author of a study in the December edition of the Journal of the American Academy of Dermatology that surveyed over 500 dermatologists to find out how they managed melanoma and how closely they followed published guidelines.
“It turns out that for melanoma in situ, only roughly two-thirds of respondents were using the recommended guidelines of excising 5 mm of the lesion,” Dr. Rigel reports. “The other one-third was taking out a larger piece.”
For thin invasive melanomas (less than 1 mm), the recommended excisional margins are 10 mm.
“However, again, only about 6 out of 10 respondents followed this guideline,” Dr. Rigel says. “The remaining dermatologists were using bigger margins.”
For thicker melanomas (greater than 1 mm), only 50% of dermatologists abided by the margin recommendation of 1 to 2 cm.
“About 33% were using a larger margin and about 1 out of 7 had less margin,” Dr. Rigel says.
The patient follow-up intervals varied as well.
“The guidelines state that patients typically should be seen once every six months for five years, then once a year afterward,” Dr. Rigel says. “Some clinicians, though, continue to see their patients more frequently and some less frequently.”
Because the melanoma guidelines are not followed to a large extent, “We either need to better educate clinicians about the guidelines or rethink the guidelines,” Dr. Rigel says.
Among the diagnostic devices being evaluated for melanoma are ultrasound, optical coherence tomography (OCT) and confocal microscopy.
“At this point, no one device has been shown to be superior to the others,” Dr. Rigel says. “But I believe that 10 years from now, we will be performing dramatically fewer biopsies as technologies become commercially available to enhance our ability to diagnose melanoma.”
Targeted therapies for different targets on the melanoma cell also hold promise.
“Up until now, we have lumped melanoma together as one disease,” Dr. Rigel says. “Eventually, though, we are going to have custom therapies for different genetic types of melanoma.”
Dr. Rigel reports that he is a consultant and an investigator for Castel Biosciences Inc.