Explaining the Gleason score: pussycats and tigers

So, unfortunately, you’ve been diagnosed with prostate cancer. You’ve read lots and now that prostate cancer is the commonest cancer in men in the West, and the second commonest cause of death from cancer. But you’re confused as you’ve also read that most men with prostate cancer die with it rather than from it, and a lot of men with prostate cancer are never actually treated but simply watched. And yet so many men die from it. Why? Well, that’s because prostate cancer is highly variable: in some men it is fairly harmless rather like a pussy cat, whereas in others it can be deadly like a Bengal tiger. And just as most cats are neither pussy cats nor Bengal tigers but somewhere in the middle, the same is true of prostate cancer. The Gleason score is the key to understanding what type of ‘cat’ your prostate cancer is.

How do we know what kind of prostate cancer you have? Well, after undergoing a biopsy a skilled pathologist will look down a microscope to examine the cells of the prostate tissue to see how aggressive it is. The pathologist then assigns a grade, the so-called Gleason score, to the cancer. The Gleason score will range from 6 through to 10 and is calculated by adding two scores together. The first score is the most frequently occurring grade across all the samples taken during the biopsy. The second is the highest grade of what’s left. When these two grades are added together the total is called the Gleason score, which is essentially a final score that captures the most aggressive rating of your prostate cancer. If you have a Gleason 9 score for example, it might be a 4+5 or a 5+4.

A Gleason score of 6 (we call this low-risk cancers) is considered relatively harmless whereas Gleason scores of 8-10 (we call these high-risk cancers) are very aggressive and almost certainly lethal without treatment. The Gleason score 7 (we call this intermediate-risk) is where it gets more complicated. This score can be made up of 3+4 or 4+3, the latter being more aggressive than the former.

So if you have a Gleason score of 8-10 you almost certainly will need treatment pretty quickly. Your urologist will arrange certain tests to check the cancer is still in the prostate and hasn’t spread to other places such as the lymph nodes or the bones. Should it have, then the best treatment is usually hormone therapy and possible chemotherapy. In a few instances, surgery might be considered only as part of a clinical study. This study is called TRoMbone and I am the Chief Investigator and would be happy to check if you are eligible if you do have metastatic prostate cancer (cancer spread to other organs). If this is the case, then please do get in touch with me.

If, on the other hand, you have Gleason 6 you are unlikely to need treatment, at least not with any urgency. However, just as not all pussycats are the same and some do bite, the same is true of Gleason 6 prostate cancer. In some cases, especially if there is a lot of cancer and you are very young or fit, then it might be better to treat the cancer now with surgery rather than watch it for years and then treat if it becomes more aggressive. A recent large study called ProtecT showed that half of all men with Gleason 6 prostate cancer needed treatment by 10 years, and that those that didn’t have treatment had twice the rate of developing spread than those that were treated. There is also the anxiety factor of knowing that you are living with prostate cancer, and having to undergo annual biopsies to keep an eye on it. Hence, I do still operate on some men with Gleason 6 prostate cancer, either because I think it’s likely it will be a future problem or because the patient chooses not to be watched.


Gleason 6

Now, if you have Gleason 7 prostate cancer, you are more likely to need treatment if it’s 4+3 rather than 3+4, but again the more cancer there is shown in the biopsies and the younger and fitter you are, the more likely it is that you should have treatment.

So, to sum up, virtually all Bengal tigers are dangerous (akin to Gleason scores 8-10) and thus need protecting from; most but not all pussy cats (akin to Gleason score 6) are harmless and thus can just be watched, and the cats in the middle (akin to Gleason score 7) are hugely variable in nature and may or may not need protecting from. Your Santis surgeon will be able to talk you through what kind of cat your cancer is like, and discuss how best to manage you.

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