Early Prostate Cancer (cont.)

How reliable are the screening tests for prostate cancer?

Neither of the screening tests for prostate cancer is perfect. Most men with mildly elevated PSA levels do not have prostate cancer, and many men with prostate cancer have normal levels of PSA. Also, the DRE can miss many prostate cancers. The DRE and PSA test together are better than either test alone in detecting prostate cancer.

A recent study examining the PSA histories of men enrolled in the Baltimore Longitudinal Study of Aging (BLSA) suggests that PSA velocity may be a better indicator of potentially life-threatening cancer than PSA level. PSA velocity is the rate at which serum PSA levels change over time. The study found that men who had a PSA velocity above 0.35 ng/ml per year had a higher relative risk of dying from prostate cancer than men who had a PSA velocity less than 0.35 ng/ml per year. More studies are needed to determine if PSA velocity more accurately detects potentially life-threatening prostate cancer early.

The NCI Early Detection Research Network (EDRN) has a Prostate Collaborative Group, which is applying a variety of strategies to find better ways to detect prostate cancer early. In addition, the NCI's prostate cancer Specialized Program of Research Excellence (SPORE) program is funding projects to identify new biomarkers to detect prostate cancer.

How is prostate cancer diagnosed?

The diagnosis of prostate cancer can be confirmed only by a biopsy. During a biopsy, a urologist (a doctor who specializes in diseases of urinary and sex organs in men, and urinary organs in women) removes tissue samples, usually with a needle. This is generally done in the doctor's office with local anesthesia. Then a pathologist (a doctor who identifies diseases by studying tissues under a microscope) checks for cancer cells.

Men may have blood tests to see if the cancer has spread. Some men also may need the following imaging tests:

  • Bone scan: The doctor injects a small amount of a radioactive substance into a blood vessel. It travels through the bloodstream and collects in the bones. A machine called a scanner detects and measures the radiation. The scanner makes pictures of the bones on a computer screen or on film. The pictures may show cancer that has spread to the bones.

  • CT scan: An x-ray machine linked to a computer takes a series of detailed pictures of areas inside the body. Doctors often use CT scans to see the pelvis or abdomen.

  • MRI: A strong magnet linked to a computer is used to make detailed pictures of areas inside the body.

Prostate cancer is described by both grade and stage.

  • Grade describes how closely the tumor resembles normal prostate tissue. Based on the microscopic appearance of tumor tissue, pathologists may describe it as low-, medium-, or high-grade cancer. One way of grading prostate cancer, called the Gleason system, uses scores of 2 to 10. Another system uses G1 through G4. In both systems, the higher the score, the higher the grade of the tumor. High-grade tumors generally grow more quickly and are more likely to spread than low-grade tumors.

  • Stage refers to the extent of the cancer. Early prostate cancer, stages I and II, is localized. It has not spread outside the gland. Stage III prostate cancer, often called locally advanced disease, extends outside the gland and may be in the seminal vesicles. Stage IV means the cancer has spread beyond the seminal vesicles to lymph nodes and/or to other tissues or organs.

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