The co-authors of Invasion of the Prostate Snatchers, blog alternate posts weekly. We invite you to post your comments.

Tuesday, September 13, 2011

“Who’s On First?” Making Sense of the Gleason Score


When you are diagnosed with prostate cancer, you need to understand the grading system that your doctor will use to recommend specific treatments. The grade indicates how aggressive the prostate cancer is, based on the pathologist’s evaluation of cancer cells taken during a biopsy. While all cancer cells look abnormal to a pathologist, low-grade cancers have cells that often look similar to healthy prostate cells. The more aggressive the cancer, the less the cells look like normal prostate cells.

Invented in 1966 by Dr. Donald Gleason, the Gleason grading system is relied on by pathologists worldwide to determine how severe your prostate cancer is. Here’s how it works:

The Gleason system assigns a grade to each of the two largest areas of cancer in the tissue samples from the biopsy. The lowest number on the Gleason grade scale is 1, and the highest is 5. The pathologist examines the biopsied tissue samples to determine where the cancer is the most prominent (the “primary grade”), and where it is next most prominent (the “secondary grade”). Then he assigns one score to the primary grade and one score to the secondary grade. The final Gleason score is the sum of these two grades. So a total score can range from a 2 (1+1) to a 10 (5+5), depending on how distorted the cancer cells look. Obviously, the lower the Gleason score, the better.

Total scores from 2 to 4 are very low on the cancer aggressive scale and, therefore, indicate that the cancer is slow growing and considered low-risk. Total scores from 5 to 6 are mildly aggressive but the cancer is still considered low-risk. A total score of 7 indicates that the cancer is moderately aggressive and considered intermediate-risk. And total scores from 8 to 10 are considered highly aggressive and the cancer is categorized as high-risk.

Hopefully you are still with me, because here comes the tricky part: In order to get clarity on your Gleason score, you need to get a breakdown of the two numbers that make up the total score—the primary grade first, then the secondary grade. The reason for this is that even when total scores are the same, not all Gleason scores are equal.  For instance, if your Gleason is 3+4=7 and your friend’s is 4+3=7, you are actually in slightly better shape than your friend. Here’s why: When the primary grade is 3, it means that the cancer cells have not deteriorated as far as the cancer cells with a primary grade of 4.

One other caveat: It is often advisable to get a second opinion on your biopsy slides, because not all pathologists are equal either. A pathologist at a world-class reference center, such as Stanford, the Mayo Clinic, or Johns Hopkins, should preferably give the second opinion, and most insurance programs will cover the cost.

Together with your PSA and tumor “staging” (more about this in my next blog), the Gleason Score is your doctor’s best shot at determining your prostate cancer’s risk factor and, therefore, your best indicator of appropriate treatment options.

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