Prostate Cancer - Screening (part4)
DRE and PSA are the 2 components necessary for a modern screening program. Transrectal ultrasound (TRUS) has been associated with a high false-positive rate, making it unsuitable as a screening tool, although it is very useful for directing prostatic biopsies.
The indications for screening are controversial. The American Cancer Society recommendations are as follows:
Both prostate specific antigen (PSA) and digital rectal examination (DRE) should be offered annually, beginning at age 50 years, to men who have at least a 10-year life expectancy and to younger men who are at high risk. Information should be provided to patients regarding potential risks and benefits of intervention.
Advocates of screening believe that early detection is crucial in order to find organ-confined disease and, thereby, impact mortality. If patients wait for symptoms or even positive DRE results, less than half have organ-confined disease. Those who do not advocate screening worry that screening will detect some cancers that are not organ confined or that it may find cancers that are not biologically significant. Currently, age-specific PSA cutoffs are used to guide screening. The trend is toward lowering the threshold level to 2.5 ng/dL, but this has not been widely accepted as yet.
Men who choose to undergo screening should begin at age 50 years. Men in high-risk groups, such as those with a strong familial predisposition (2 or more first-degree relatives are affected) and those of African American race, should begin screening at a younger age (40-45 y). These men are less likely to have the latent form of the disease and benefit from treatment. More data on the precise age to start prostate cancer screening are needed for men at high risk.
Recent data from Canadian and Austrian studies suggest that mortality rates are lower as a result of PSA screening. Canadian data have shown that from 1989-1996, the mortality rate was lower in the PSA-screened cohort than the control group. Recent studies from Tyrol, Austria also show a beneficial result for screening in reducing disease-specific mortality. These beneficial effects are likely due to the fact that treatment rather than observation may enhance disease-specific survival. This was recently shown in a 2002 Scandinavian study that reported significantly reduced disease-specific mortality for radical prostatectomy patients when compared with watchful waiting. No difference in overall survival was noted. Currently, US data have shown a decrease in mortality of 1% per year since 1990, which coincides with the advent of PSA screening. Other theories have been proposed to account for the decrease, and these include changing treatment practices and artifacts in mortality rates secondary to the changing incidence.
Abnormal rectal examination findings
Findings from the DRE are crucial. An irregular, firm prostate or nodule is typical, but many cancers are found in prostates that feel normal. Pay careful attention to the prostate consistency, along with the seminal vesicles and adjacent organs, to detect spread of the disease to these structures.
Overdistended bladder due to outlet obstruction
- Neurologic findings secondary to cord compression: Other subtle findings, such as paresthesias or wasting, are uncommon.
- Lower extremity lymphedema
- Supraclavicular adenopathy
- Lower extremity deep venous thrombosis
- Cancer cachexia
Transrectal ultrasound
TRUS is used to examine the prostate for hypoechoic areas, which are commonly associated with cancers but are not specific enough for diagnostic purposes. At least 6 or, more recently, 10 or more systematic biopsy specimens of peripheral and, occasionally, transitional zones are taken under ultrasound guidance. Samples should include most areas of the gland, irrespective of ultrasonographic abnormalities.
Differential diagnosis
Benign prostatic hypertrophy
Calculi
Prostatic cysts
Prostatic tuberculosis
Prostatitis
© Dan Theodorescu
© Tracey L Krupski