Prostate Specific Antigen in prostate cancer diagnosis. How to use PSA correctly? 12
How to use PSA correctly for prostate cancer screening. High PSA levels are different in young and older people. Prostate MRI without contrast to screen for prostate cancer. Dr. Anton Titov, MD. PSA is controversial in prostate cancer diagnosis. Guidelines seem to change just about every year. How PSA can be used in men in general population, in high-risk population, or in surveillance for prostate cancer diagnosis? What is your personal point of view on PSA use in prostate cancer? Dr. Mark Emberton, MD. We all blame PSA in prostate cancer diagnosis. The problem isn’t with PSA. The problem is with what we did after PSA. PSA, as long as you don’t do a biopsy, is a fantastically powerful predictor of survival in prostate cancer. We know this from the Swedish studies that we’ve done. These were cardiological studies done 40 – 50 years ago. And blood was preserved. From blood samples we’ve been able to ascertain PSA levels. And those “cohorts matured”. It means that all people in the clinical study died. We know what they’ve died of. If your PSA is less than 1, your chances of dying of prostate cancer is infinitesimally small. So low PSA is good. And what it also told us is this. If you are young and have a PSA that is around 2, you might also have a problem. So PSA as a predictor. PSA is a prognostic marker of what might happen in the future. It is hugely valuable. Dr. Anton Titov, MD. Once you start doing a test like trans-rectal biopsy, which is riddled with imprecision, the role of PSA diminishes. Dr. Mark Emberton, MD. Change that to today, MRI allows you to adjust for prostate volume, which is a key driver of PSA. Prostate MRI also allows you to see whether there’s a cancer or not within the prostate. MRI allows you to do an accurate prostate biopsy. PSA might work much better because of the performance test. PSA works better with the verification that you’re doing afterwards. So I think we have to look at PSA again. The function of PSA is being determined by what we do after it. We’ve just discussed that MRI has changed dramatically. It may be now that PSA is a useful early cheap test to identify a cohort of men that can subsequently be diagnosed with prostate cancer. One caveat is this. If you do enough MRIs on enough people, you soon find men who have quite large prostate cancers with very low PSAs. While it will certainly improve the performance of PSA, PSA might not be the perfect test. PSA has sensitivity. It can identify the real cancers that are out there, and miss very few. It may be that MRI without the injection can be done easily to screen for prostate cancer. This is controversial. MRI without contrast is completely passive test. You have to do only “T2 sequences”, which are the anatomical sequences. And you do diffusion sequences, which can be done in about 10 minutes, maybe 15 minutes. It is MRI without IV contrast because it’s a completely passive test. No IV contrast, no doctor present during such MRI. Dr. Mark Emberton, MD. You could have your MRI in the supermarket. You don’t need a physician present. It might be a very cost-effective test done once in a lifetime. In the way that we do a flexible sigmoidoscopy, or colonoscopy now, around 55 years of age. This predicts whether or not you are likely to get colon cancer and to die of colorectal cancer. So this is something we wish to explore. We’ve put in a couple of grant applications on this very topic of using MRI to screen for prostate cancer. They’ve all been rejected. But I think with time it will be tested. Dr. Anton Titov, MD. So PSA, in conjunction with MRI, and in conjunction with active surveillance and clinical opinion might be the best use of PSA. Dr. Mark Emberton, MD. I think so, yes.
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