Men who use phosphodiesterase 5 (PDE5) inhibitors for erectile dysfunction are feared to be at higher risk of melanoma, but it is unclear whether this is causal or related to sun exposure.
To investigate, researchers from the London School of Hygiene and Tropical Medicine used national data to compare 145,104 men prescribed PDE5 inhibitors with 560,933 unexposed men.
They found a weak association between PDE5 use and malignant melanoma (hazard ratio 1.14, 95% confidence interval 1.01–1.29; P=0.04). However, there was a similar increase in risk for basal cell carcinoma and solar keratosis, linked strongly to sun exposure. Solar keratosis was also associated with subsequent PDE5 inhibitor use.
In PLoS Medicine (online, 14 June 2016)
, the researchers say the results strongly suggest that the risk of melanoma is driven by increased sun exposure among men who use PDE5 inhibitors.
 Matthews A, Langan S, Douglas I et al. Phosphodiesterase type 5 inhibitors and risk of malignant melanoma: matched cohort study using primary care data from the UK Clinical Practice Research Datalink. PLoS Medicine 2016;13(6):e1002037. doi: 10.1371/journal.pmed.1002037