The current Gleason grading system recognises three patterns or grades of cancer. These are given a number 3 to 5. However, the pattern of any one cancer can be mixed and the prognosis for any patient depends upon this mixed pattern. The two most common patterns are each given a separate number and then the two numbers are added to give the Gleason grade, for example 3+4=7. The Gleason grade can therefore be between 6 and 10.
A Gleason grade or score 3+3=6 tumour has a relatively good prognosis and is often just monitored, a Gleason 7 tumour is intermediate and a Gleason 8 to 10 has a poor prognosis. In the Gleason 7 category a Gleason 4+3=7 tumour is a worse tumour than a Gleason 3+4=7 as there is more Gleason 4 pattern than 3 pattern.
As well as the pattern of the growth or tumour, the extent of the cancer felt on digital rectal examination (DRE) is also important in estimating a prognosis. The extent of cancer is referred to as the stage. Stage 1 (T1) cancers cannot be felt on DRE, stage 2 (T2) cancers can be felt, but still feel to be within the prostate, stage 3 (T3) are felt to have extended outside the prostate and stage 4 (T4) are felt to be well outside the prostate, invading adjacent organs such as the bladder or pelvic wall.