Prostate Cancer Differential Diagnosis
Not all patients with an elevated PSA concentration have CaP. Other factors that elevate serum PSA include BPH, urethral instrumentation, infection, prostatic infarction, or vigorous prostate massage. Induration of the prostate is associated not only with CaP, but also with chronic granulomatous prostatitis, previous TURP or needle biopsy, or prostatic calculi. Sclerotic lesions on plain x-ray films and elevated levels of alkaline phosphatase can be seen in Paget disease and can often be difficult to distinguish from metastatic CaP. In Paget disease, PSA levels are usually normal and x-ray findings demonstrate subperiosteal cortical thickening.
The case for CaP screening is supported by the following: The disease is burdensome in this country; PSA improves detection of clinically important tumors without significantly increasing the detection of unimportant tumors; most PSA-detected tumors are curable; prostate cancer mortality is declining in regions where screening occurs; and curative treatments are available. Although the benefit of screening was recently shown in one randomized Canadian study, several questions have been raised about the data analysis (Labrie et al, 1999). Two large randomized clinical trials to assess the benefit of screening are ongoing. In the Prostate, Lung, Colon and Ovarian Trial (PLCOT), 74,000 men have been randomized to annual DRE and PSA screening versus no screening. Results are anticipated in 2006. A larger trial involving 190,000 men in the European Randomized Study for Prostate Cancer Screening is anticipated to provide results in 2008. The efficacy of treatment is being examined in Scandinavia, where two randomized trials compare watchful waiting with radiation therapy or radical prostatectomy. A similar trial, Prostate Cancer Intervention Versus Observation Trial (PIVOT), is under way in the United States. Such trials, although imperfect, may give us the information we need before prostate cancer screening and treatment can be recommended with confidence.
In summary, many factors must be considered by both clinicians and their patients who are contemplating screening for prostate cancer. The information provided should attempt to answer such questions as the likelihood that an unscreened asymptomatic man will be adversely affected by prostate cancer in his lifetime, whether the screening test will lengthen or improve the quality of life, the chances of having a false-positive result and its consequences, the value of a normal result, and the recommendations of various experts. Based on available data, our bias has been that relatively young, healthy, asymptomatic men are encouraged to undergo screening. Screening is highly encouraged in certain populations with a higher disease prevalence or higher mortality rates, such as African American men or men with a significant family history of CaP. If CaP is detected, patients are carefully counseled regarding the benefits and risks of all treatment options, including watchful waiting. At the present time the data suggest that if screening is done, the combination of DRE and serum PSA is best.
Revision date: June 20, 2011
Last revised: by Amalia K. Gagarina, M.S., R.D.