What is prostate cancer?

The former US president, Joe Biden, recently revealed that he has been diagnosed with prostate cancer that has spread to his bones. It’s a stark reminder of a disease that kills one man every 45 minutes in the UK - and yet, prostate cancer still lacks the public visibility of breast or lung cancer. The wrinkle doctors are grappling with, though, is that almost every man living to 80 will develop prostate cancer in his lifetime; but the majority will never know and it will never be a problem for them. And detecting and treating a non-problem can only cause problems, whether from side effects or mental disquiet of being labelled with a disease. So, in this programme, we’re attempting to get underneath this conundrum, beginning by exploring what prostate cancer actually is, how it spreads, and - perhaps more importantly - what is being done to improve screening tools, and develop more targeted treatment. Professor Mark Emberton is a prostate cancer specialist based at University College London. Chris Smith started by asking him who the typical prostate cancer patient might be…

Mark - Typically it's a man just over 65. I think 67 is the most common age at which we diagnose prostate cancer. Usually, there are no symptoms, and so they have presented as a result of a positive blood test—something we call a PSA—which puts them at higher risk than the average man of their age.

Chris - And you say no symptoms. Is that part of the problem here?

Mark - It is. Once prostate cancer causes symptoms, you've got a problem. It usually means that the cancer is invading local structures—rectum, which sits just behind the bladder—causing problems with urinating. But that's a very, very late presentation. Or even worse, as we've recently seen in the news, the cancer has spread beyond the prostate to bone and lymph nodes.

Chris - And what actually is this cancer? I mean, when one looks at this cancer in the prostate, what is happening? Where is it coming from? And what's it doing?

Mark - So, the prostate is a gland. It makes semen. None of us would be here if the prostate didn’t exist. It sits just below the bladder and just in front of the rectum, tucked away behind the pubic bone—the hard bone you can feel just above the penis. So it's quite a hard-to-reach organ. The prostate sits there quietly for most of one’s life. It can grow in a benign fashion—we call that benign prostatic hyperplasia—and it can cause problems urinating or emptying the bladder by squeezing the urethra or water pipe.

Prostate cancer develops in most men over time. If you look at the prostates of men aged 80 who die of something else, you’re more likely than not to find small amounts of prostate cancer within that prostate. That’s been known for a long time. We know that the generation of cancer develops over time. What we understand less well is why, in some men, that process is accelerated and the cancer becomes aggressive—hence, the capability of spreading beyond the prostate to other organs, and resulting in death if left untreated.

Chris - What are the risk factors for it? Who's most at risk? Is there nothing you can do to prevent it?

Mark - It’s not linked to smoking or alcohol, but we do know quite a few things. Maleness, obviously, is critical. Age is hugely important. I think age gives the cells in the prostate the opportunity to undergo sequential genetic mutations. These are little errors where the DNA is copying itself. Prostate cancer doesn't result from one error—it's usually lots and lots of little errors that probably accumulate over time. We know a little bit about epidemiology—the big picture stuff.

If people move from an area of low cancer incidence, such as South Asia, to America, within a couple of generations they approximate the risk we normally associate with Americans. Black men, for instance, are at greater risk. We don’t exactly know why.
It may be genetics, but we don’t understand that fully. It may be lifestyle issues, diet, or vitamin D—through the reduced ability to absorb sunlight.

But it’s poorly understood. That’s pretty much it. There’s an interesting trend: as you move away from the equator, especially in the northern hemisphere, the incidence increases.
So, there’s nothing you can do to prevent it, and therefore, the only strategy we really have is to detect it early.

Chris - And what sorts of numbers are we talking about? If you take a country like the UK—although you've said it's very common with age, presumably we’ve got an ageing population, we’re seeing more cases—but how many cases do we get? And how many men die every year because of this?

Mark - It’s very common, but fortunately, not many men die of it. That’s the really important bit of news to take away from this. But having said that, about one in eight men in the UK today will be diagnosed with prostate cancer during their lives. About 12,000 men die every year. The good news is that death rates have reduced over the last decade by about 10%, largely due to improved treatments. There has been a dramatic improvement in how we manage prostate cancer—from diagnosis to very late-stage disease.

We used to say that a man had a 3% lifetime risk of dying of prostate cancer—so a one in 30 risk. That’s probably now close to—not quite, but close to—a one in 60 risk. So there’s a huge discrepancy between prevalence, which is very dependent on how we define the disease, and the proportion of men who will die from it.

Chris - Why do you think, given that it is so common, we don't have a screening programme for it in the same way that we have one for breast or cervical cancer?

Mark - We've tried many times. The UK and USA have run large screening studies. Hundreds of thousands of men have been randomised to early detection programmes versus standard care.
And the results have been very disappointing.

Chris - Was that because people didn’t live any longer? Or we over-treated people?

Mark - Yes. In many studies, there was no difference in mortality. Some showed a very small difference—so men who are screened have a slightly lower chance of dying of prostate cancer—but at huge cost in terms of the number of men biopsied and the number likely over-diagnosed. This is a difficult concept, but it refers to someone being given a diagnosis that has no impact on their overall survival. I believe there’s only one country in the world with a formal screening programme—I think that’s Lithuania. No other country believes the evidence is strong enough to justify one. I think that's because we've been using the wrong tools—PSA and an inaccurate biopsy method. All the studies have used that method. We’re now poised to see if we can detect cancer early using today’s tools, which are much more accurate.