Assessing Prostate Cancer Risk

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Assessing Prostate Cancer Risk

There are a number of factors that urologists and radiation oncologists take into account when they try to determine how serious a prostate cancer is for an individual patient. Patients are usually given this information when they are told that the biopsies are positive for cancer. Based on these factors it is possible to assign patients to risk groups and estimate the chance of long-term cure. There are also tables and computer programs called nomograms that use these risk factors to make predictions about the extent of the cancer and the chances for long-term cure.

Prostate Cancer Risk Factors

Stage

The stage of a cancer is a statement by the physician regarding how much cancer is present and if the cancer has spread beyond the prostate. Because we are able to use PSA testing we find most prostate cancers before they spread to other organs. There are a number of different staging systems for prostate cancer. The Jewett system is an older system which assigns a stage from A to D. It has largely been replaced by the AJCC TNM system, which assigns a T stage for the cancer in the prostate, an N stage for cancer in lymph nodes, and an M stage if there are metastases, or spread of cancer to other organs. In this system cancers picked up by an elevated PSA are called T1C cancers, and have a higher chance of cure than cancers picked up by a palpable nodule. Cancers which are palpable in one side of the prostate, but don’t seem to spread outside the prostate, are called T2A and cancers palpable in both sides are called T2B. Cancers which obviously spread outside the prostate are called T3 cancers, and these cancers have a much lower chance of cure than T2 cancers.

Grade (Gleason Score)

The grade of a cancer is determined by the pathologist when he looks at the prostate biopsy under the microscope. The grade, or Gleason score, in an indicator of how aggressive the prostate cancer may behave. The Gleason score can theoretically range from 2-10, with a higher number indicating a more aggressive cancer. In practice, we never see scores less than 6, so the scoring system really goes from 6 to 10. Cancers given a Gleason score of 6 are usually slow growing and have a high chance of cure. Cancers given a score of 7 are unpredictable, but some can be aggressive cancers. Cancers with Gleason score 8 or higher are serious cancers that need prompt treatment, but these high-grade cancers can be cured if they are caught early.

PSA

The PSA is a good indicator of the amount of prostate cancer present. The lower the PSA at the time of diagnosis the higher the chance for cure. Many men have their cancer detected because the PSA test is elevated, usually when it is between 4 and 10. An elevated PSA in this range is still quite low, and men with prostate cancer which has spread to other parts of the body usually have a PSA of 50 or higher.

Number of positive biopsies

The number of positive biopsies is an indicator of cancer volume. Most urologists biopsy 8-12 different areas of the prostate. Patients in whom more than 1/3 of the biopsies are positive have a lower chance of cure than men with fewer positive biopsies.

DNA analysis

DNA analysis is a test that can be performed on the prostate biopsy by the pathologist who reads the biopsies. It usually involves a measurement of the amount of DNA, or genetic material, in the cancer cells. Cancers in which the cells have normal DNA are more curable than cancers with abnormal DNA. There is usually a good correlation between the DNA analysis and the Gleason score. Most Gleason 6 cancers have normal DNA, and almost all Gleason 8 or higher cancers have abnormal DNA. The DNA analysis can give important information about the risk of Gleason 7 cancers.

Presence of perineural invasion

Perineural invasion occurs when cancer cells spread along nerve cells in the prostate. It is possible that the cancer cells spread along the nerves on the way out of the prostate. If a small nerve in the prostate is captured in the biopsy the pathologist may see perineural invasion. This is usually the sign of a more agressive cancer, and is common in cancers with a higher Gleason score and rare in Gleason 6 cancers.

Ultrasound appearance

The ultrasound appearance may give the urologist important information about the extent of the cancer. In many cases the cancer can be seen on ultrasound, and the urologist may see evidence that the cancer is spreading into or through the capsule of the prostate. However, many cancers are not able to be seen on ultrasound. The ultrasound also gives important information about the prostate size and shape.

Staging Tests

Staging tests are x-rays which are done to determine if the prostate cancer has spread beyond the prostate. In most cases of prostate cancer these tests are not necessary, because the chance that the cancer has spread is very low (see calculators of prostate cancer outcome below). Staging tests are not usually done if the PSA is less than 10.

Patients with a higher risk of spread of cancer require imaging tests to determine if there is spread of cancer beyond the prostate. Patients with spread of cancer on imaging tests have advanced prostate cancer, and will require some type of medication to shrink and control the cancer. The two most common imaging tests are the bone scan and the CT scan. The bone scan is a nuclear medicine test which takes an image of all of the bones in the body. It can pick up cancer in the bones before it is visible on plain x-rays, but it may also show arthritis or other bone problems. A CT scan is used to look at lymph nodes in the pelvis and abdomen which may be enlarged if they contain cancer. MRI testing of the prostate can be performed in unusual cases, but it has not been shown to be very accurate and is not available in most areas. MRI of bones which are suspicious on bone scan is sometimes helpful.

Prostate Cancer Risk Groups

Based on the risk factors discussed above prostate cancers can be assigned to risk groups which have different chances for cure. There have been a number of risk groups systems proposed, but a commonly used one is as follows:

Risk Group	Risk Factors
Very Low risk	Stage T1C (diagnosed by elevated PSA only) Gleason Score 6 or less PSA less than 10 Fewer than 3 biopsy cores positive, < 50% cancer in each core PSA density < 0.15 ng/mL/g
Low risk	Stage T2A or less Gleason Score 6 or less PSA less than 10
Intermediate Risk	One adverse risk factor: Stage T2B, or Gleason Score 7, or PSA 10-20
High Risk	Two or more adverse risk factors from intermediate risk group Stage T3a or higher Gleason score 8-10 PSA greater than 20

Very low risk group cancers make up approximately 40% of prostate cancers detected by screening. The NCCN recommends that all very low risk prostate cancers be managed by active surveillance, or observation. If there is any evidence of cancer growth then treatment can be safely given at that time without increasing the risk of death from prostate cancer.

Low Risk cancers have a high chance of cure (>90%) with any of the standard treatments.

Intermediate risk cancers have a lower, but still reasonable, chance of cure (70-80%) with any of the standard prostate cancer treatments.

High-risk cancers include patients with cancer that has spread, or metastasized, beyond the prostate and also includes men with high-risk cancers that appear to still be contained in the prostate. High-risk cancers that have obviously spread beyond the prostate are treatable, and most men live many years, but most of these cancers cannot be completely cured. Men who have high-risk cancers that appear to still be confined to the prostate may still be cured by aggressive treatment, but frequently benefit from treatment with multiple modalities (i.e. surgery followed by radiation treatments, or radiation and hormonal therapy or chemotherapy).

Calculators of Prostate Cancer Outcome

The Partin Tables are a set of tables that estimate the chances that a cancer has spread beyond the prostate to the seminal vesicals or lymph nodes. It uses the cancer stage, Gleason score and PSA.

Prostate Calculator was developed using a computer technology called neural networks and is actually several calculators that estimate the risk of spread of cancer outside the prostate or to the pelvic lymph nodes, and the chance of cure for patients who have undergone surgery.

Memorial Sloan Kettering Cancer Center nomogram was one of the first nomograms to compare the chance of cure following surgery, brachytherapy, and external beam radiation. It uses cancer stage, grade, and PSA. You may need your doctor to give you some of the information regarding radiation dose to get accurate predictions about long-term cure.

Carlos G. Arcangeli, MD & Mark A. Rosen, MD