In recent years researchers have uncovered a potentially important pathway whereby PDE5A inhibitors (which include sildenafil-- Viagra-- and other drugs used to treat erectile dysfunction and pulmonary hypertension) could potentially increase the risk of developing melanoma. Now a new study provides early evidence showing an association between sildenafil and melanoma, though, like all observational studies, it is unable to demonstrate a cause-and-effect relationship.
The study, published in JAMA Internal Medicine, analyzed data from more than 25,000 men who participated in the Health Professionals Follow-up Study. Men who had recently used sildenafil had nearly twice the risk of developing melanoma after adjusting for other risk factors (hazard ratio 1.84, CI 1.04 - 3.22). Men who had used sildenafil at any time had a similar increase in risk. No increase in risk was observed for other skin cancers (basal cell carcinoma and squamous cell carcinoma) without known links to PDE5A inhibitors. In addition, there was no significant association between erectile function by itself and melanoma.
The investigators did not explore whether other PDE5A inhibitors, including tadalafil (Cialis) and vardenafil (Levitra), were associated with melanoma, since these drugs were not available at the start of the study. But in their discussion they point out that because these drugs are longer-acting they may potentially result in an even greater increase in risk for melanoma.
Because the study was a retrospective, observational study, the authors cautioned that their findings "should be interpreted cautiously and are insufficient to alter current clinical recommendations."
In an accompanying editorial, June Robinson agrees with the authors that a prospective study will be required before clinical recommendations should be changed. But she sees little reason why physicians should not perform melanoma screening when writing a sildenafil prescription for older men who have a history of sunburns. Early detection, she noted, "may make melanoma a curable disease."
