Prostate cancer diagnosis

Current diagnosis of organ-confined prostate cancer

Physical examination of the prostate and/or a blood test are routinely performed to detect early organ-confined prostate cancer (PCa).

  • The digital rectal examination (DRE) assesses the size, shape and texture of the prostate via the rectum.
    DRE
  • The blood test determines the level of prostate specific antigen (PSA) present.
  • Suspected PCa (based on a suspicious DRE and/or elevated PSA) is typically confirmed by prostate biopsy. During a prostate biopsy, small samples of prostate tissue (usually from 6-12 different regions/cores) are removed by inserting a biopsy gun with a needle in the prostate through the rectum. The tissue is examined under the microscope for cancer cells. Prostate biopsies are routinely performed on an out-patient basis and rarely require hospitalisation.

PSA-DRE-Biopsy

If cancer cells are found in the biopsy tissue, the Gleason score (ranging from 2-10) is determined by the pathologist. Men with a Gleason score ≥ 7 have a worse prognosis / outcome than men with a Gleason score < 7.

Current problems in the diagnosis of early organ-confined prostate cancer

Interpretation of PSA test results

PSA levels below 4 ng/mL are usually considered normal. However, this also depends on age. The age-specific upper limits of normal for Caucasians are shown in Table 1 (http://www.pccnc.org/early_detection/psa/). A PSA above these levels can trigger prostate biopsy as it may indicate PCa.

 

Table 1: Age-specific upper limits of normal for PSA
Age (years) PSA in blood (ng/mL)
40-49 2.5
50-59 3.5
60-69 4.5
70-79 6.5

 

PSA is not a perfect test.

  • Men with a PSA level below the age-specific limit of normal can have PCa.
  • Moreover, many men with a PSA level between the age-specific upper limit of normal and 10 ng/mL will not have PCa. This is due to the fact that PSA is not cancer-specific and is produced by both cancerous and non-cancerous prostate cells. As a result, men with benign prostate diseases such as benign prostatic hyperplasia (BPH, i.e. prostate enlargement) or prostatitis (infection of the prostate) will have an elevated PSA (higher than 2.5-4 ng/mL). The greater the number of prostate cells / size of the prostate, the higher the PSA level in the blood.

Prostate biopsy may cause pain, bleeding and infection. Therefore, there is a need for additional tests that will help avoid unnecessary biopsies.

Interpretation of biopsy test results

  • A prostate biopsy samples less than 1% of the total prostate which can result in missing substantial PCa. This may falsely reassure the patient and physician. Therefore, it is sometimes required to obtain a second series of biopsies.
  • On the other hand, a positive biopsy may detect a small volume, non-significant or indolent cancer that is not life-threatening and can lead to unnecessary treatment or over-treatment. Results of the biopsy specimen are used for pre-operative staging and are thus important for PCa prognosis and deciding whether the detected PCa warrants early treatment, usually removal of the total prostate (i.e. radical prostatectomy). Unfortunately the correlation between pre-operative staging and staging after removal of the total prostate (i.e. post-operative staging) is relatively poor, probably due to the described sampling errors during the biopsy procedure. Between 10-30% of prostate cancers are pre-operatively estimated to be worse than they really are (i.e. over-staged cancer).

These patients may receive a radical prostatectomy, even though their cancer would not likely have ever threatened their life or even caused symptoms. Furthermore, they are subjected to the side effects of prostatectomy (often including incontinence and impotence). Over-treatment presents one of the largest challenges Urologists face today.

National Cancer Institute

Wikipedia