(NBC News) -- Women who take a regular dose of aspirin may get a side benefit – a reduction in their risk of melanoma, a new study suggests.
And the more years women take the over-the-counter-medication, the lower the risk, according to the study which was published online today in Cancer.
"We think our results are very exciting and that they add to the growing body of evidence suggesting that aspirin may have some real anti-tumor and anti-cancer properties," said study co-author Jean Tang, an assistant professor of dermatology at Stanford University.
Tang and her colleagues scrutinized data from 59,806 Caucasian women who were taking part of the Women's Health Initiative study. The women, who were between 50 and 79 years old at WHI's outset, were followed for an average of 12 years. The researchers chose to concentrate on Caucasian women because melanoma is much more common among them.
At the beginning of the study, the women were asked which medications they were taking, what they ate and what activities they participated in.
The women in the asprin group took a dose of aspirin at least twice a week at baseline. When they were asked about aspirin use again three years later, 60-70 percent of the group were still taking it at least twice a week, Tang says.
Overall, women who used aspirin had a 21 percent lower risk of melanoma compared to those who eschewed the medication. The longer women used aspirin, the lower the rate of the potentially fatal skin cancer. So, those who had used aspirin for one to four years had an 11 percent reduction in risk, as compared to 30 percent among those taking aspirin for five or more years.
In their calculations, the researchers took into account numerous melanoma risk factors, including differences in pigmentation, tanning practices, sunscreen use.
The researchers don't know how aspirin lowers melanoma risk, but they've got some theories.
"Aspirin reduces inflammation," Tang said. "Cancer cells with a lot of inflammation grow more and are more aggressive." Tang added that cancer cells tend to produce in excess the very same substance that aspirin and other NSAIDs knock back.
The researchers failed to find a reduction in risk with other NSAIDs, however.
The new study, coupled with earlier evidence, makes a good case for aspirin's anti-cancer properties, experts said.
Still, the effect may not be strong enough to counter aspirin's possible side effects for people who have been told they shouldn't take the medication, said Dr. Robert Stern, a professor of dermatology at Harvard Medical School and chief of dermatology at the Beth Israel Deaconess Hospital. Stern co-authored a study published in 2011 that also found that aspirin reduced melanoma risk by 50 percent.
But for those who are sitting on the fence as to whether they should take aspirin for prevention of heart disease, this new research might be enough to push them over the edge since the benefits would now potentially be two-fold.
"I think it is too early to tell women to change their behavior, unless they would be taking it for the cardiovascular benefit also," said Dr. Jenny Kim, an associate professor of dermatology at the David Geffen School of Medicine at the University of California, Los Angeles. "Before we can recommend that patients start taking aspirin to prevent melanoma we need to have some randomized controlled trials."
