How Prostate Cancer is Graded

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Grading a cancer is a method doctors use to evaluate a patient’s prognosis and determine the best management strategy. The higher the grade, the more aggressive the cancer’s behavior. The Gleason grading system is used for prostate cancer, with a pathologist assigning the grade after reviewing a prostate biopsy slide.

The Gleason system assigns a number from 6 to 10 to indicate the cancer’s aggressiveness. This number is actually the sum of two scores, each ranging from 1 to 5: a primary score, which describes the relative abnormality of the cells making up the largest area of the tumor, and a secondary score, which describes the cells of the next largest area. Gleason score 6 cancers tend to behave less aggressively than Gleason score 7 cancers, which, in turn, are not as aggressive as cancers scored 8, 9, or 10.

Today, 60 percent to 70 percent of cancers diagnosed by way of a prostate biopsy are graded as Gleason score 6; about 20 percent to 30 percent, Gleason score 7; and 5 percent to 10 percent are Gleason 8 and higher.

The Gleason score is not the only result you may see on your pathology report. Many pathologists also use a grading system from the International Society of Urological Pathology (ISUP). Your urologist will assist you with understanding the significance of all this information.