Predictive tool for prostate cancer treatment
Every year, tens of thousands of men are diagnosed with cancer of the prostate, the gland that sits at the base of the bladder. But what should they do about their condition? Should they elect to have radiotherapy, or surgery, and risk the side effects of the treatment? Or should they instead choose just to monitor the disease and treat any symptoms as they occur, because - in their case - they’re actually more likely to die of some other disease before the prostate cancer actually causes a problem?
This is the quandary faced by patients every day. But now researchers in Cambridge have developed a predictive tool that uses various measurements from a patient to calculate the benefit to them, in terms of how their life expectancy may change, if they do - or do not - decide to treat the disease. It’s called Predict Prostate, and Chris Smith went to talk to one of the brains behind it...
Vincent - My name is Vincent Gnanapragasam I'm a consultant urologist in the University of Cambridge. We have produced a new tool that will help men newly diagnosed with prostate cancer to decide whether or not treatment is right for them and to help them make decisions whether these treatments are going to benefit or whether or not they won't.
Prostate cancer is a very common disease, and as we men get older that is a disease which is almost inevitable in some cases. But not all prostate cancers will go on to cause problems or indeed result in cancer-related death. In fact, you're more likely to live with it than to die from it. So we set out to understand what are the attributes of these cancers which we can actually identify which informs an individual when they’re newly diagnosed about whether or not they need treatment up front.
Chris - When we are considering prostate cancer, how many cases are there in a country of the sort of size of the UK and our population demographic at the moment?
Vincent - Well, at the moment, we are diagnosing approximately 40,000 men with prostate cancer every year, and we know that the data projections are that by 30 years time we are actually going to be diagnosing about 70% more. We’re also getting much better at picking it up, and picking it up at an early stage, and all of this is going to result in many men being diagnosed with prostate cancer and potentially living with their diagnosis.
Chris - One of the questions that always goes with a screening programme is if we look for something we've got to be able to do something about the thing we are looking for and do something about it in a good way. So do you know that when we do intervene in prostate cancer we are actually improving the prognosis for that person? We’re not just labelling someone now you've got prostate cancer, now you live with all these side-effects we've inflicted on you, but actually we've not really changed the outcome of that person; they're not gonna live any longer?
Vincent - So that is at the heart of the Predict Prostate tool. The key point is what do you do with a new diagnosis, and Predict Prostate was constructed to actually help an individual understand that if you have a new diagnosis you may need treatment because you can see clear benefits from that, but in some cases you may not see a huge benefit from that. And it also then gives confidence, we hope, that they can live with that slow-growing indolent cancer which is unlikely to cause a problem, but they can know that with a little bit more surety than just by being told by someone that that's the case.
Chris - How did you design this model or how did you create this?
Vincent - We took a population dataset from the East of England of 10,000 men and we used statistical models which had been developed by our collaborators to actually construct the model. And then we re-tested it in a cohort from Singapore which is ethnically different and showed that the model actually proves to be quite accurate in that setting as well.
Chris - So what factors specifically about an individual if someone walks into your clinic can you make measurements? What factors are you considering so that the model can make these predictions?
Vincent - One of the basic things you wanted to do as to make it accessible to anyone, anywhere. That means we have to use the clinical data that is available - a patient’s age, PSA blood test value...
Chris - That's Prostate Specific Antigen, that’s a blood marker that can indicate something is up with the prostate, can't it?
Vincent - You're absolutely correct. And that is used as a detection test but actually the level also has some value in predicting outcome. Then we look at this stage, how extensive is the cancer, and what the sample showed when we took the biopsy or piece of the prostate, and how many of those biopsies are positive. Those in the essential elements and they are available in any standard consultation. We were amazed actually by how powerful just those simple factors could be if put together in the right way.
Chris - So you are saying you take those measurements and you can make prediction of what exactly with those numbers?
Vincent - So what the model is telling you is what the impact of these factors are on someone's overall risk of dying. And so the model tells an individual what the 10 and 15 year survival chances are with and without treatment measured against that.
Chris - Do you think on the basis of being in this position now with a much more powerful tool that we now have in the form of models like yours that we should be pushing for some kind of screening programme for prostate cancer? Because we have screening programmes for breast cancer, we have screening programmes for cervical cancer and they're very effective, but the numbers of people afflicted with those conditions are very low compared to the numbers that you've been saying are affected by prostate cancer. So at what point do you think we need to start well we need to do something about this?
Vincent - So the paradigm needs to shift. Screening is all about saving lives, so effectively if you look at the mantra about screening you have to show that an intervention improves survival. And so you have this problem with overtreatment which is why people don't want to screen for prostate cancer. So I think that if there is an acceptance that you can pick up lots of cancers which don't need treatment, but which you can monitor and that becomes okay, then I think screening programme will become effective.