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Study Associating Viagra Use to Melanoma Risks is a Significant Red Flag

Is Viagra worth a higher risk of Melanoma?  A recent study may lead some Viagra users to ask this question.        

Pfizer has reportedly collected about two billion dollars in revenues in each of the past three years from sales of its prescription drug Viagra.[1]  That’s a staggering $6 billion since 2011.  Although Viagra is a widely distributed drug, it is an elective drug advertised to treat erectile dysfunction (ED).      

Melanoma, on the other hand, is a major public health problem.[2]  It is the deadliest type of skin cancer.[3]  In 2012, the estimated amount of new cases of Melanoma in the United States was 76,000.[4]  More than 9,700 people are expected to die from melanoma in the U.S. each year.[5]

In April 2014, the Journal of the American Medical Association (JAMA) published the results of an alarming study that associates an increased risk of melanoma with Viagra use.  The Viagra-Melanoma Study is entitled Sildenafil Use and Increased Risk of Incident Melanoma in U.S. Men, A Prospective Cohort Study.  Viagra is the brand name for the drug sildenafil.[6]     

This study of nearly 26,000 men associates Viagra use with an increased risk of developing Melanoma.[7]  For users of Viagra, a “PDE5A inhibitor”, the study “provide[s] epidemiological evidence on possible skin adverse effects.”[8]  “[The study’s] findings suggest an association of PDE5A inhibitors with the risk of melanoma development.”[9]   

Researchers from the Harvard Medical School analyzed data from the Health Professionals Follow-Up Study (HPFS), specifically the association between Viagra use for ED and the risk of incident melanoma.[10]  The HPFS began in 1986 when 51,529 U.S. male health professionals, aged 40 to 75 years, completed a questionnaire on their medical history and lifestyle practices.[11]  Biannually, those surveyed complete additional follow up questionnaires.[12]  Those surveyed have been predominantly white males with only 531 African-Americans and 877 Asian-Americans.[13]  Melanoma is over 20 times more common in Caucasians than in African-Americans.[14] 

The Viagra-Melanoma Study compared the distribution of characteristics between Viagra users and nonusers.[15]  The study excluded surveyed individuals with complicating characteristics, such as non-white patients, those with cancer diagnosis at baseline, or others with missing birth dates.[16]  After careful exclusions, researchers still had 25,848 participants remaining to analyze.[17] 

For participants who used Viagra at any time (“ever use”), they were associated with a higher risk of melanoma (HR 1.92; 95% CI, 1.14-3.22).[18]  The “HR” is the Hazard Ratio value, also known as the “relative risk.”  A relative risk is the risk that one might experience the negative effect studied when compared to the general population.  Said differently, a relative risk of 1.0 means that the occurrence of the negative effect in the study population is equal to the expected occurrence rate of the effect in the general population.  With a Hazard Ratio of 1.92, the study shows an increased risk of melanoma for Viagra users when compared to the general population of non-Viagra users.  The amount of the relative risk, 1.92, is close to a doubling of the relative risk.  

In secondary analysis, there was more than a doubling of the risk.  The association between sildenafil use and melanoma was even more significant when excluding outcomes occurring in the first 2 years (HR 2.19; 95%CI, 1.18-4.07), and excluding all users of other treatments for ED (HR 2.18; 1.15-4.15).[19]  When excluding participants with major chronic diseases at the time when data was first gathered (baseline), “ever use” of sildenafil was associated with an even higher risk of melanoma (HR 2.77; 95% CI, 1.32-5.85).[20] 

The researchers were careful to rule out and consider potential study pitfalls.  For example, they made certain to check whether melanoma was simply associated with ED itself.[21]  They also confirmed that “sildenafil use was associated exclusively with melanoma” as opposed to non-melanoma skin cancer, “indicating that [their] findings were less likely due to sun exposure, physical examinations, or detection bias.”[22]  According to the researchers, “together, these results suggest an association between sildenafil use and melanoma, regardless of other characteristics.”[23]           

The study is particularly important given the wide use of ED drugs.  “Since the approved use of sildenafil in 1998 and vardenafil hydrochloride (Levitra) and tadalafil (Cialis) in 2003, PDE5A inhibitors have remained the first-line therapy for ED.”[24]  Although widely used now, ED drug use may expand further.  Pfizer’s Viagra use patent is set to expire in 2020, meaning generic versions of the drug, which are typically less expensive, will enter the market in upcoming years.[25]  As part of a settlement, Pfizer competitor Teva Pharmaceuticals USA, Inc. will be allowed to launch a generic version of Viagra in the U.S. in December 2017 or earlier.[26]  The introduction of cheaper alternatives to brand name ED drugs may result in increased ED drug availability and use, making the potential melanoma risk even more important to address as soon as possible.        

 


 

[1] PFE Fin. Rpt. at 117 (2013).
[2] Li et al., Sildenafil Use and Increased Risk of Incident Melanoma in US Men, JAMA Intern. Med. at E2 (Pub. Online Apr. 7, 2014) (hereinafter “Viagra-Melanoma Study”).
[3] http://www.webmd.com/melanoma-skin-cancer/melanoma-guide/default.htm.
[4] www.cancer.org; Viagra-Melanoma Study at E2.
[5] Id.
[6] Id.
[7] See generally Viagra-Melanoma Study.
[8] Id. at E6.
[9] Id. at E5.
[10] Id. at E2.
[11] Id.
[12] http://www.hsph.harvard.edu/hpfs/hpfs_about.htm.
[13] Id.
[14] http://www.cancer.org/cancer/skincancer-melanoma/detailedguide/melanoma-skin-cancer-key-statistics.
[15] Viagra-Melanoma Study at E3.
[16] Id.
[17] Id.
[18] Id.
[19] Viagra-Melanoma Study at E3.
[20] Id.
[21] Id. at E5.
[22] Id.
[23] Viagra-Melanoma Study at E5.
[24] Id. at E4.
[25] PFE Fin. Rpt. at 105 (2013).
[26] Id. 

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