Last year, a report highlighted a potential link between use of erectile dysfunction drugs, like Viagra, and melanoma. The news caused quite a stir, but in reality the findings are likely just a correlation mishap. Writing in the Journal of the American Medical Association, researchers at NYU Langone Medical Center found no such evidence when they systematically combed through the records of 20,235 mostly white Swedish men. Instead, the observed incidence, which is quite striking, is likely due to socio-economic factors (men who take Viagra are generally better off, and can afford vacations in sunny locations where they risk getting skin cancer) than a cause-effect relationship between Viagra and skin cancer.
In 2014, 142 cases of men who had taken Viagra and been diagnosed with melanoma were reported. Stacy Loeb, an urologist at New York University, wasn't convinced though. She assembled a team and began doing their own research. The team tapped a Swedish healthcare database, given that the records are extremely well put together featuring instances of disease, treatments, but also lifestyle choices. Among the 20,235 records of Swedish men, the researchers found 435 of them had filled at once for a Viagra subscription or substitute (Levitra, Cialis).
Initially, Loeb alarmingly noticed that those men who had tried the erectile dysfunction drugs bore a 21% higher risk of malignant melanoma. This seemed to confirm the hyped findings performed earlier by the other group. Loeb's decided to look at other metrics, in case they missed some important association or lack thereof. Indeed, they found that those men who had ingested more Viagra didn't show an increased risk of developing skin cancer. In medicine, there is this "dose relationship" effect which says the more of disease-causing drug is ingested the greater the risk of developing that affliction. This wasn't the case. Next, the researchers also looked at the "dose-response." Basically, the higher the half-life of a drug (the time it takes to get flushed out of the body), the greater the risk of developing an associated disease. Of the three erectile dysfunction drugs, Cialis has the long half-lime. Once again, there was no particular difference in risk of developing melanoma between the individuals taking the other two drugs.
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This likely settles it: viagra doesn't cause skin cancer. Still, those people stuck with melanoma aren't a fabricated statistic - their condition is real. So what's causing it? Loeb notes that those men who get melanoma tend to have higher disposable incomes and education levels. In other words, they can afford more lavish vacations in exotic locations where there's plenty of sun. To be sure this wasn't just a hunch, the team also screened for another skin cancer called basal cell carcinoma. They found the same risk as in melanoma (19 to 21%), but basal cell carcinoma works with different biological pathways than those involved in PDE5i use and malignant melanoma. PDE5i is short for phosphodiesterase type-5 inhibitors, the active substance in the erectile dysfunction drugs. If theoretically melanoma could have been biologically triggered by Viagra, there's no way the drug could have produced basal cell carcinoma.
"What our study results show is that groups of men who are more likely to get malignant melanoma include those with higher disposable incomes and education—men who likely can also afford more vacations in the sun—and who also have the means to buy erectile dysfunction medications, which are very expensive," says lead study investigator and NYU Langone urologist Stacy Loeb, MD, MSc."While medications for erectile dysfunction come with serious risk of a drop in blood pressure if taken together with other medicines called nitrates, overall they are safe medications, and our results suggest that physicians should not be concerned that the drugs cause melanoma," says Loeb, an assistant professor at NYU Langone and member of its Perlmutter Cancer Center.
