SAN FRANCISCO (CN) – Pushing back on claims that Viagra and Cialis accelerate the progression of skin cancer, an oncologist testified Thursday that she studied the data and found no plausible link between the erectile dysfunction drugs and melanoma.
"Every week I have a patient with melanoma who is taking these medications," Dr. Lynn Schuchter said. "If I thought this medication increased their risk of getting melanoma, I would tell them to stop."
Schuchter, a professor and practicing oncologist at the University of Pennsylvania, said she reviewed seven studies on more than 4 million patients and found all but one resulted in risk estimates close to "1," which is not statistically significant.
A 2014 study by Dr. Wen-Qing Li of Brown University found patients who took sildenafil, the active ingredient in Viagra and Cialis, had an 84% increase in the risk of developing or accelerating melanoma. However, subsequent studies resulted in lower estimates for risk increases of 1% to 25%.
Schuchter said the subsequent studies show "science really worked" here because a hypothesis was made in one study and later proven wrong.
"There is no evidence that showed these medications make melanoma progress," Schuchter said.
When asked why each study showed at least some increased risk of accelerating melanoma progression, the doctor explained there were "confounding factors" for patients, the primary one being sun exposure.
She cited a 2019 study, which found patients who took Viagra and Cialis had a higher risk of getting basal cell carcinoma, a different type of skin cancer, but "there is no biological plausibility that these medications can cause basal cell cancer," she said.
"That tells me there is more sun exposure for men who are taking medications like Cialis and Viagra," Schuchter explained.
Addressing a study investigating whether phosphodiesterase type 5 (PDE5) inhibitors in Viagra and Cialis can be used to treat skin cancer, Schuchter said that experiment never would have been done if the scientific community believed the medications could harm patients.
"You wouldn't treat a patient with a drug that makes melanoma worse," Schuchter said.
The results of that experiment showed the treatment was tolerated, or caused no significant side effects, and did not cause rapid progression of melanoma.
"I don't think these medications will be anti-cancer agents, but I think it showed these medications are safe and didn't accelerate melanoma," Schuchter said.
On cross-examination, plaintiffs' lawyer Jennifer Liakos of Napoli Shkolnik in Los Angeles asked questions to demonstrate that Schuchter is not an epidemiologist trained to investigate the causes of diseases, and that the oncologist has never conducted an epidemiological experiment herself.
Liakos then showed Schuchter six peer-reviewed research papers which stated there was a "plausible biological mechanism" linking the active ingredient in Viagra and Cialis to melanoma progression.
Schuchter replied that those papers merely referenced findings from prior studies, and none of them found a plausible link based on their own research.
"You're reading epidemiological studies that have referenced the preclinical studies," she said.
Liakos next showed Schuchter a study that found a 24% increase in the risk of developing lung cancer for women exposed to secondhand smoke, a risk factor similar to those found in studies on the link between the erectile dysfunction drugs and melanoma.
Schuchter was the first of four experts to testify on behalf of pharmaceutical firms Pfizer and Eli Lilly in a four-day causation hearing. U.S. District Judge Richard Seeborg must decide if the science underpinning claims that Viagra and Cialis cause skin cancer progression is adequate to justify a jury trial. The plaintiffs presented the first of their three expert witnesses on Tuesday.
More than 800 lawsuits have been filed against the two pharmaceutical firms and consolidated in a multidistrict case in San Francisco.
Both sides are expected to present closing arguments on Oct. 22.
Follow @NicholasIovino
Subscribe to Closing Arguments
Sign up for new weekly newsletter Closing Arguments to get the latest about ongoing trials, major litigation and hot cases and rulings in courthouses around the U.S. and the world.
