Viagra to Fight Cancer? (Plus an 'Immensely Embarrassing' Story)

David J. Kerr, CBE, MD, DSc


October 15, 2020

This transcript has been edited for clarity.

Hello. I'm David Kerr, professor of cancer medicine from University of Oxford. Today I'd like to comment on an interesting paper I picked up recently in Nature Communications. The authors looked at phosphodiesterase-5 inhibitors, their use, and their impact on risk and mortality from metastasis in male patients with colorectal cancer.

Phosphodiesterase-5 inhibitors to you and me are Viagra-like drugs, which are used to treat erectile dysfunction. It was a careful study, using the Swedish Cancer Registry and the Swedish Prescribed Drug Register. They did two things: First, they used a tissue database to look at the impact of phosphodiesterase-5 expression on outcomes from 430 cases of surgically dissected colorectal cancer.

Phosphodiesterase-5 expression has a marginally bad effect in terms of prognosis. The higher the expression of the enzyme, the worse the prognosis was. There were small numbers and the P values were very marginal, so the data are not terribly convincing.

Then they did what they do best, which is to go back to the population-based registers. Over the period of study, looking at colorectal cancer mortality as the primary outcome and patterns of metastasis as a secondary outcome, they compared and contrasted the general male population during the study period with the 1100 or so men who had been using a variety of these different types of phosphodiesterase-5 inhibitors.

There was an improvement in colorectal cancer mortality and what seemed to be a reduction in metastases to solid organs, to liver and to lungs, but not to lymph nodes. It's moderately plausible that there is some emergent evidence from murine studies and limited studies in man, suggesting that these drugs can have an impact on immune function and stimulating immune function.

We know that certainly, postoperatively, there can be a loss or a degree of immunosuppression. Therefore, by using these drugs, hypothetically at least, it might cause a degree of immunostimulation that could lead to some form of reduction in metastasis or improvement in mortality.

Of course, the authors say at the end that this opens the possibility of us doing randomized trials of these drugs postoperatively. They discussed a whole host of technical questions about how often the drugs were used and what sort of pattern of prescribing. Can individuals in Sweden get access to the drug privately, just buying them directly from websites rather than being prescribed? It's an interesting observation.

This allows me to segue into my own story, in that I've only ever used Viagra once in my life. This was years ago. I was very friendly with one of the inventors of the drug. I was scoffing at his — in those early days — imagined properties. He gave me one which, as men do, I put in my wallet and forgot about it.

About a year later, I was asked to speak at a very distinguished Burns supper in Scotland. Our national bard, Robert Burns, is our most famous poet; we remember his birth date every January. It's a fantastic ceremony in which we dress up in kilts and traditional Scottish gear. We toast our great bard. We remember him through song, through recitation of his poetry, and a particular type of food that we eat — haggis — for the uninitiated. It's a wonderful night.

I decided, peculiarly, before this Burns supper, that I would take half of one of these Viagra tablets, which I did. Two things happened. One, my nose got blocked up. I guess there's a degree of nasal congestion, which made my speech sound rather funny. That was part of it.

Secondly, you know the old question "What do Scotsmen wear under their kilts?" With the friction of the heavy tartan and the bumbling around of my sporran bashing into parts of me...well, the drug worked. I was in an unfortunate situation of having to stand at the top table to give my talk with my sporran pushed to one side, and with me protruding somewhat through my kilt. I had to hide my erection behind the menu and the running order for the Burns supper, to my immense embarrassment, trying to hide it from all and sundry.

There you are — two stories for the price of one. One, a moderately interesting observation that is moderately plausible, linking phosphodiesterase-5 inhibitors to improved outcomes in early-stage colorectal cancer, and then my one story of sildenafil use, never again to be repeated.

Thanks for listening, as always. I am interested in any comments whatsoever. For the time being, Medscapers, over and out.

David J. Kerr, CBE, MD, DSc, is a professor of cancer medicine at the University of Oxford. He is recognized internationally for his work in the research and treatment of colorectal cancer and has founded three university spin-out companies: COBRA Therapeutics, Celleron Therapeutics, and Oxford Cancer Biomarkers. In 2002, he was appointed Commander of the British Empire by Queen Elizabeth II.

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