SAN FRANCISCO—Good news for men who have undergone prostate cancer treatment: Using Viagra won't increase their risk of the disease recurring.
Researchers said here at the Genitourinary Cancers Symposium that studies have found no association between patients who take phosphodiesterase type-5 inhibitors such as Viagra (sildenafil) and Cialis (tadalafil) and an increased risk of prostate cancer recurring.
If anything, the evidence—although not statistically significant —seems to indicate that taking the drugs that help men overcome erectile dysfunction might even be protective, said Stacey Loeb, MD, Assistant Professor of Urology and of Population Health at New York University.
“This is very good news for men,” Loeb told OT at her poster presentation. “The bottom line here is reassurance. We don't think these should be a change in clinical practice. Guys shouldn't be worried. Doctors shouldn't avoid prescribing these drugs. They are generally safe and well-tolerated.”
Loeb said she and her colleagues decided to perform their study following the appearance of two studies in Europe. “It was a big surprise when the study from Germany came out a couple of years ago suggesting that the men who took Viagra had an increased risk of prostate cancer recurrence and there was a lot of hesitation of whether those results were true,” she said. “Then a study from a single center in Italy didn't find a relationship, so we wanted to be the tiebreaker.”
To do that, Loeb went to colleagues at the Karolinska Institute in Sweden and paired with them to access the National Prostate Cancer Register of Sweden, which is linked to the nation Prescribed Drug Register.
The researchers identified 293 men who had radiation therapy or radical prostatectomy from 2006 to 2007, then experienced biochemical recurrence after treatment. “For each case, we identified 20 controls who were biochemical recurrence-free at the event date of the index case, using density sampling stratified by age at diagnosis and treatment, developing a control group of 5,767 men.”
The researchers then employed multivariate condition logistic regression to examine the relationship between phosphodiesterase type-5 use with biochemical recurrence.
No Relationship Found
“We looked at the database covering the entire country of Sweden, so we were able to look at all prescriptions for phosphodiesterase type-5 inhibitors across the country,” she said. “That eliminates all kinds of recall bias. After you adjust for confounding factors, there is no relationship between phosphodiesterase type-5 inhibitors and prostate cancer recurrence.”
In the model using diagnostic variables, it appeared that as more pills were used, the less a risk of recurrence developed compared to men who were not using the phosphodiesterase type-5 products. If the men were using below the median number of pills counted cumulatively, their risk of recurrence was 12 percent less than the non-users, but that difference did not attain statistical significance, Loeb said. “If there is a signal, it is one that the drugs may be protective rather than harmful,” she said.
If the men were using more than the median, the reduction in risk was 32 percent and was statistically significant...until prostatectomy variables were added to the equation, when the difference was reduced to 27 percent, but that also was not statistically significant, she pointed out.
In the study, 248 cases were men who had prostatectomy, and 137 (or 55%) used phosphodiesterase type-5 inhibitors. They were paired with 4,886 controls who had undergone surgery and 3,061 (or 63%) had used the pills.
Another 45 cases had been treated with radiotherapy; 13 of them (31%) had relied on the pills. They were paired with 881 men and 273 (27%) had used phosphodiesterase type-5 inhibitors.
“Our patient population included men who had prostatectomy and those who had definitive radiation therapy,” Loeb said. “It didn't matter what form of initial therapy they had. Using the drugs did not result in a greater risk of prostate cancer recurrence.”
A second study presented at the meeting also found essentially the same thing (Abstract 119). Using the Cancer of the Prostate Urologic Research Endeavor (CaPSURE) database, researchers from the University of California at San Francisco compared 3,089 men who had used phosphodiesterase type-5 inhibitors and 758 men who were not exposed to the medications.
After more than 70 months of follow-up, the researchers reported in their poster that “phosphodiesterase type-5 inhibitor usage was not associated with biochemical recurrence following treatment for prostatectomy or radiation therapy.”
The research team also found a non-significant difference, which, if anything, favored use of the pills as being protective.
“Phosphodiesterase type-5 inhibitors should not be withheld due to concerns that it increases the risk of disease recurrence,” the researchers wrote in their presentation.
The findings resonated with other clinicians. Mitchell Anscher, MD, Professor of Radiation Oncology at Virginia Commonwealth University in Richmond, told OT, “We haven't looked specifically at our patient population, but based as to what is out there in the literature, I always reassure guys, ‘if you need it, use it. Don't worry about it. It is not going to affect your treatment or the cancer.’
“Easily more than 60 percent of men who have prostate cancer already have erectile dysfunction,” he said. “It's nice to see another study that is confirming that it is okay to do. The study does not show a statistically significant difference, but if anything the patients on the phosphodiesterase type-5 inhibitors are doing better. So there isn't anything detrimental.”
Added Oliver Sartor, MD, the Laborde Professor of Cancer Research at Tulane Cancer Center in New Orleans, “The three things that men worry about after prostate cancer treatment is recurrence, incontinence, and erectile dysfunction.
“These studies show that if you address the question of erectile dysfunction, it does not affect the risk of recurrence,” he told OT. “This is a reassuring safety message. This is a big deal for patients and for urologists. This is a good thing for people to know.”