STAGING PROSTATE CANCER: PSA AND STAGING
We know PSA can signal the presence of cancer. But can PSA be more specific—can it tell a doctor the stage of a man’s tumor? Yes, it can. However, as always, PSA is tricky, and the PSA level alone doesn’t tell the whole story.
As a tumor gets bigger, the PSA level generally goes up. And, as the tumor grows, it tends to be overrun by the more malignant, poorly differentiated cancer cells. These poorly differentiated cancer cells elevate PSA less per gram of tissue than well-differentiated cancer cells. Therefore, the PSA level doesn’t go up in a directly corresponding way.
That’s why PSA can be normal even when cancer has spread to the seminal vesicles or pelvic lymph nodes, or it can be higher than expected in men with cancer that’s confined to the prostate. So, the true meaning of PSA can’t be interpreted without knowing the Gleason score.
Scientists at Johns Hopkins have found a more accurate way to estimate the exact extent of prostate cancer, using a special table that correlates clinical stage, Gleason score, and PSA (see table 3.3).
Even though prostate cancer may appear to be confined to the prostate on examination, surgery may reveal a different story – often, the cancer turns out to be more extensive than it seemed at first. That’s because insidious, microscopic bits of cancer can sneak past the prostate wall, and these can’t always be found with the digital rectal exam, biopsy, transrectal ultrasound or other diagnostic methods.
Because surgery is only indicated for the cancers that truly are localized to the prostate, it would be better for everyone to know before the operation how extensive the cancer is.
So, how to predict which cancers may have spread beyond the prostate wall? Tables 3.3a—3.3d were developed by Johns Hopkins researchers after a study of the course of prostate cancer in 1,186 men who had radical prostatectomy.
The tables are designed to help you and your doctor predict your definitive pathological stage and best course of treatment. For example, if you have stage T2a disease, with a Gleason score of 5 and a PSA less than 4, there is an 81 percent chance that the cancer will be completely confined to your prostate. On the other hand, if your Gleason score is 8 and your PSA is is, the likelihood drops to 29 percent. With this information and an estimation of your overall health and longevity, you and your doctor can decide whether or not it’s reasonable to select curative forms of therapy, or simply to adopt a policy of watchful waiting, in which the tumor is treated only after it produces symptoms.
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