It would be helpful if we had more accurate indicators of severity for men with newly diagnosed prostate cancers. Our treatment decisions, and even whether to pursue treatment at all, are currently based on inadequate data. If we were better able to predict which cancers are likely to remain quiescent and which are likely to progress, many men would not have to undergo treatment and could thereby avoid complications such as incontinence and impotence. The fact that we do not have valid indicators of severity results from the failure of prostate cancer research (see Chapter 14).
Additional predictors of severity are available from prostate biopsies but are underutilized. These include information on the number of specimens (cores) positive for cancer, the percentage of each positive core occupied by cancer, and the percentage of Gleason grade 4 or 5 cells in each core. For example, my own biopsy included 9 probes, 5 on the right side (where the cancer had been felt) and 4 on the left side. On the right, 3 of the 5 had cancer, and on the left 0 of 4 did. Thus, overall, 3 of 9 were positive.
Several studies have reported that the percentage of biopsy probes that are positive for cancer is a better predictor of recurrence than the PSA level. In a large study of 1,149 prostate cancer biopsies, only 1 core was positive for cancer in 47 percent of cases; 2 in 24 percent; 3 in 18 percent; and 4 or more in 11 percent. One study focused specifically on Gleason 7 cancers and reported that when one third or fewer cores were positive for cancer, chances of cancer recurrence after surgery were significantly lower than if one half or more cores were positive. Another study reported that the percentage of biopsy cores positive for cancer was the best predictor of cancer recurrence for men undergoing beam radiation treatment.9
Biopsy reports also usually include information on what percentage of each positive core is occupied by cancer cells. In two of my positive cores, cancer involved 20 percent of the specimen; in the third core, it involved 5 percent. Furthermore, Gleason grade 4 cells occupied 40 percent of the cancer in one core, 20 percent in another core, and there were no grade 4 cells in the third core. Studies suggest that the percentage of cancer in the positive cores and the percentage of the cancer that is Gleason grade 4 and 5 cells are both predictive of outcome. One study reported that if cancer in any positive core occupies more than 50 percent of the core, the chances of cancer recurrence is 15 percent higher at five years and 30 percent higher at ten years than if the cancer occupies less than 50 percent of the core.10 And for Gleason 7 cancers, the greater the percentage of grade 4 cells in the positive cores, the more serious the cancer.
Attempts to identify additional and more accurate indicators of severity in newly diagnosed prostate cancers continue. Such indicators include specific proteins in the blood and urine, as well as measurement of genes that have become activated; these will be discussed in Chapter 15. Advances in this research area could profoundly affect how we treat prostate cancer.
In summary, the best predictors of having prostate cancer and of the severity of such cancers are the following:
• PSA level: below 4 is favorable; 4-10, you have a 25 percent chance of having cancer; 10-20, you have a 50 percent chance of having cancer; the higher the level over 20, the greater the chance of your having cancer and the more serious the cancer is likely to be.
• Free PSA: the lower the free PSA as a percentage of total PSA, the more likely it is that you have cancer; over 25 percent is a good sign; under 10 percent is not a favorable sign.
• PSA velocity: the faster the PSA rises, the more likely it is that you have cancer; a very rapid increase in PSA suggests a rapidly growing cancer. In order for this measure to be useful, you must have had multiple PSA measurements over time.
• If the cancer is large enough to be felt on digital rectal exam, that is not a favorable sign.
• The larger the size (volume) of the cancer, the more serious it is likely to be.
• If cancer is felt in only one-half of one lobe of the prostate, that is good. If it is felt in both halves of one lobe, the outlook is not quite so favorable. If it is felt in both halves (both lobes) of the prostate, that is less favorable.
• A Gleason score (the combination of two numbers) of 5 or less is very good. A score of 6 is still good. A score of 7 (3+4) or 7 (4+3) is not as good, but the seriousness depends on the percentage of grade 4 cells present. A score of 8 or more is not favorable.
• Each biopsy consists of a number of cores. The fewer cores positive for cancer, the better your chances of having a curable cancer.
• Each biopsy core that has cancer is assessed for the percentage of the total core that is cancerous. If the core that has the most cancer has less than 50 percent, that is good.
• Any sign of spread of cancer outside the prostate is definitely not favorable.
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