Sildenafil and Melanoma Risk
Sildenafil may be associated with increased melanoma risk, according a recent study published in JAMA Internal Medicine.
However, a cause and effect relationship has not been found and there is not enough evidence to warrant treatment changes.
Sildenafil is a phosphodiesterase (PDE) 5A inhibitor that is frequently prescribed to men with erectile dysfunction. It is the active ingredient in Viagra.
Previous lab research conducted in vitro has shown that PDE5A inhibition could spur the development of melanoma cells and melanoma cell invasion.
For this study, the research team, led by Dr. Wen-Qing Li of Brigham and Women’s Hospital (Boston, USA) and Harvard Medical School, looked at data from the Health Professionals’ Follow-Up study, which started in 1986. This biennial health survey included men between the ages of 40 and 75.
Specifically, the researchers analyzed data from 25,848 men recorded between 2000 and 2010. The men’s mean age was 64.8 years. Recent sildenafil use (during the previous three months) was reported by 5.3% of the men; 6.3% had used it at some point in the past.
Over this period, 142 cases of melanoma, 580 cases of squamous cell carcinoma, and 3,030 cases of basal cell carcinoma (all types of skin cancer) were reported.
The researchers found that men who took sildenafil – either recently or ever – were at higher risk of developing invasive melanoma. They were not at higher risk of developing the other types of skin cancer, however.
Media reports have suggested that the risk of skin cancer increases by 84% for men who take sildenafil. As Daniel Pendick explained in a recent Harvard Health Blog post, this statistic is misleading, as it refers to the relative risk, comparing two specific groups - the study’s participants who did not take sildenafil and the participants who did.
The absolute risk, Pendick notes, is 0.43%, meaning that the number of cases per 1,000 men increased from 4.3 among the men who didn’t take sildenafil to 8.6 among the men who did.
Other erectile dysfunction drugs, such as tadalafil (Cialis) and vardenafil (Levitra) were not included in the study, as they had not been approved when the research began.
The authors noted that future studies might examine different populations, different dosing regimens, longer follow-up periods, and latency of exposure.
“Our results should be interpreted cautiously and are insufficient to alter current clinical recommendations,” they wrote. “Nevertheless, our data provide epidemiological evidence on possible skin adverse effects of PDE5A inhibitors and support continued investigation of this relationship.”
In a JAMA Internal Medicine Invited Commentary, Dr. June K. Robinson recommended that physicians screen men for melanoma when writing prescriptions for sildenafil. Older men with a history of serious sunburns are among the most vulnerable.
Additional training on melanomas might be required for some physicians, but the end result could be quite beneficial, Robinson explained. For example, after eight hours of training in Germany, a group of primary care physicians screened men for melanoma and decreased mortality from 1.9/100,000 men before screening to 1.0/100,000 men after screening.
“Early detection, which may make melanoma a curable disease, may be achieved by physicians performing screening in the at-risk population for melanoma,” Robinson wrote.