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Histologic Grade of Prostate Cancer

The grade is a measure of how mutated the cells have become. Cancer of a glandular organ (an organ that produces a substance, in this case semen) is called ADENOCARCINOMA. The closer the cancer cells look like normal gland cells (well differentiated) the less serious (less likely to spread and slower growing.)

The more mutated the cells become (moderately then poorly differentiated) the more serious. (see Gleason Scoring System). The grade is ranked from 1 to 5 and since there may be more than one pattern the next most common pattern is graded and the two numbers are added to get the Gleason Score. So the lowest score (and most slow growing) would be 2 and the highest score (most fast growing or dangerous) would be 10.
 
See pictures of typical  Gleason 6 (3+3), Gleason 7 (3+4), Gleason 7 (4+3) and Gleason 8 (4+4). Also since the most common pattern is listed first, a Gleason 7 that was calculated as 4+3 is worse then one calculated as 3+4 (since it had more of the 4 pattern than the 3, see data for surgery  here and here and for seeds). Seeds alone may not be good for a 4+3 unless seeds are combined with external or hormones (go here). There is some evidence that if there is a third type (called tertiary) then is should be added if the Gleason is a 5 (go here).

Grade Distribution (National Data)
well differentiated 21%
moderately differentiated 56%
poorly differentiated 23%
 

More recently the Gleason scoring system has been used. The cells are scored from slowest growing, well differentiated (grade 1) to the worst (fastest growing, most poorly differentiated grade 5.) The biopsy is graded twice (if there is a secondary pattern it is scored or if only one pattern it is scored twice.) The total score then can range from a low of 2 (best) to 10 (worst.) The relationship between Gleason and Grade is as follows:

well differentiated Gleason 2,3,4
moderately differentiated Gleason 5,6,7
poorly differentiated Gleason 8,9,10


The outcome is markedly influenced by the grade. In the large RTOG 94-13 study using radiation the relapse rate was as follows:

well differentiated 10% relapse
moderately differentiated 55% relapse
poorly differentiated 70% relapse
 

In a large series (500 cases) reported from the Mayo Clinic the relapse rate by Gleason Score:

Gleason score 2,3,4 6% relapse
Gleason 5,6 15% relapse
Gleason 7 33% relapse
Gleason 8, 9, 10 56% relapse

Large Radiation Series (563 cases, Cancer 1998;83:971) the control rate at 5 years (bNED) by Gleason Score
Gleason Score Control at 5 Years
2 - 4 78%
5- 6 63%
7 37%
8 - 10 33%
 
The Gleason Score is critical in deciding whether any treatment is necessary. In an elderly patient with a slow growing cancer (Gleason score of 2 or 3) simple observation (called conservative therapy) may be appropriate. A recent study (JAMA 1998;280:975) in men aged 55 to 74 who did not receive active therapy for their prostate cancer, looked at the odds of dying of cancer in 15 years based on their Gleason score as noted:
Untreated Prostate Cancer
Gleason Score Death by 15 Years
2 - 4 4 - 7%
5 6 - 11%
6 18 - 30%
7 42 - 70%
8-10 60 - 87%

Survival by Gleason Score after Radiation (RTOG Data)

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Valicenti. J Clin Onc 2000;18:2740


Survival by Gleason Score after Surgery

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