Cases of melanoma among U.S. adolescents and young adults declined markedly from 2006 to 2015 - even as the skin cancer's incidence continued to increase among older adults and the general population during the span, new research in JAMA Dermatology shows.

The finding, based on national cancer-registry data, suggests that public-health efforts advocating sun protection are changing behaviors among Millennials and Post-Millennials, the investigators surmised.

"There seems to be a breakthrough happening that might really reverse the trend for increasing melanoma incidence," says Margaret Madeleine, MPH, PhD, a co-senior author of the study and an epidemiologist at the Fred Hutchinson Cancer Research Center in Seattle, in a news release.

"The vast majority of my practice is older and middle-aged adults, but absolutely melanoma can affect younger patients," says Jennifer Gardner, MD co-senior editor of the study and a clinical assistant professor of medicine (dermatology) at the University of Washington School of Medicine in Seattle. "I do have patients who are in the prime of their life and otherwise healthy, and they're thinking about other things and bigger ambitions, and unfortunately this diagnosis really hits them quite hard."

The researchers gathered de-identified patient data of 988,000 invasive melanoma cases from databases at the Centers for Disease Control and Prevention and the National Cancer Institute. In analyzing data, the investigators calculated annual percentage of change for multiple demographics, including age: pediatric (ages 0-9), adolescent (10-19), young adult (20-29), and adults in 10-year increments from 30 to 80+.

"We were wondering, with the advent of public health programs to increase sun protection - sunscreen and hats and staying in the shade and all the recommendations for skin cancer prevention - if that effort is working. Is there a corresponding decrease we can see reflected in melanoma rates?" adds Madeleine.

The researchers found that, across all ages, the number of melanoma cases rose steadily during the study span, from 50,272 in 2001 to 83,362 in 2015. The overall increasing incidence rates seen over time was primarily driven by adults 40+ years, the authors wrote.

However, for adolescents and young adults, incidence peaked around 2005 and then fell sharply through 2015: Among males, the incidence rate dropped about 4 percent per year and, among females, about 4.5 percent per year across the two age groups.

The drop-off mirrors reductions in melanoma rates seen among younger populations in Australia starting around 1988, the authors wrote. They attributed that nation's turnaround to public-health campaigns for sun-protective behaviors, including a "Slip! Slop! Slap!" campaign.

In the United States, Gardner said, "we're doing a better job of treating more advanced types of melanoma, but we are still seeing it increasing overall, so the (public health) work is not done. More efforts for prevention make a lot of sense."

This work was supported in part by National Institutes of Health grants P30CA015704, T32CA009515, T32CA092408, and T32CA009168; the Fred Hutchinson Cancer Research Center Integrated Immunotherapy Research Core; and a Society for Immunotherapy of Cancer–Merck fellowship.