Prostate Cancer Laboratory and Other Diagnostic Tests
Alternate Names : Adenocarcinoma of the Prostate
Prostate Cancer Laboratory and Other Diagnostic Tests
Recent advances have been made in the clinical screening for prostate cancer. Because prostate cancer frequently occurs as an occult condition, may be curable when still localized to the gland, and remains resistant to cure when locally advanced (extending beyond the capsule of the gland) or metastatic to pelvic lymph nodes, distant organs, or bones, there is strong motivation to improve the early detection capability. Annual digital rectal examination (DRE) and serum prostate-specific antigen (PSA) determination remain the chief components of screening recommendations by the American Urological Association and the American Cancer Society. Onset of screening is recommended for all men over the age of 50 years. For black men and men with a family history of prostate cancer, onset of screening is recommended at age 40.
DRE is a simple procedure whose sensitivity for prostate cancer is 86% but whose specificity is only 44%. The rate of detection of prostate cancer by DRE alone in asymptomatic men ranges from 0.2% to 2.2%.
PSA is a serine protease found exclusively in benign and malignant prostate tissue. Elevation of serum PSA may occur in BPH, inflammation or infection of the prostate, or prostate cancer. PSA elevations above 10 ng/ml usually reflect malignant disease of the gland and are rarely observed in individuals with benign conditions. PSA determination with a value of 4 ng/ml as an upper limit of normal provides a 79% sensitivity and a 59% specificity for the detection of prostate cancer. The rate of detection of prostate cancer using PSA determination alone in asymptomatic men is 2.2% to 2.6%. Estimates of PSA concentration in prostatic tissue (PSA density), the rate of rise of PSA values over time (PSA velocity), or the creation of age-specific normal reference ranges for PSA may have greater discriminatory value for cancer detection, particularly for men with PSA values in the troublesome range of 4 to 10 ng/ml.
Transrectal ultrasound (TRUS) is a screening method whereby an endorectal probe housing an ultrasonic transducer is inserted into the rectum overlying the prostate gland. The transducer allows imaging of the prostate for echogenicity, which permits localization of areas suspected for malignancy. Hypoechogenic areas in the peripheral zone of the prostate may be identified that are suspected for malignancy and that may be biopsied for histopathologic confirmation of cancer. As an isolated screening tool, TRUS detects prostate cancer at a rate of 1.7% to 20.6% in screened men. The disadvantages of TRUS include its relatively low sensitivity and specificity for the detection of cancer, its expense, and its requirement for a physician sophisticated in its use. The utility of TRUS derives from its ability to detect nonpalpable cancers, its use as an adjunct to DRE in evaluating palpable lesions, and its ability to enhance the accuracy of biopsy of suspected prostatic lesions.
Serum prostatic acid phosphatase determination was widespread as a screening test before the advent of PSA in clinical practice. The prostatic acid phosphatase value is normal in approximately 57% to 75% of men with localized prostate cancer. Prostatic acid phosphatase testing has been largely supplanted by PSA as the screening test of choice.
The diagnosis of prostate cancer is based on the careful histopathologic examination of prostate resection specimens or specimens collected from prostate biopsy. In the examination of tissue obtained from patients with suspected localized prostate cancer, Gleason scoring should be sought. The probability of extension of cancer beyond the prostatic capsule and into pelvic lymph nodes increases with increasing Gleason score. Once the diagnosis of prostate cancer is confirmed by histopathologic examination, noninvasive evaluation of the patient for metastatic disease should be conducted. The radionuclide bone scan is the most sensitive method for the detection of bone metastases, the most common site of extrapelvic advanced disease in the prostate cancer patient. Plain x-rays of bone in areas showing uptake of radionucliude should be obtained, particularly if in weight-bearing sites or if correlated with pain. Metastasis to visceral or solid organs is relatively uncommon in prostate cancer, whereas metastases to pelvic and abdominal lymph nodes is a frequent route of dissemination. In the 25% of men with metastatic prostate cancer who have pulmonary metastases, routine chest x-ray is a useful procedure. Chest x-ray may not only delineate pulmonary abnormalities but may also detect bone metastases. Computed tomography (CT) and magnetic resonance imaging (MRI) are relatively expensive, low-yield, and insensitive screening procedures for detecting advanced prostate cancer at these sites. PSA determination may be used in the therapeutic management of prostate cancer. Failure of an elevated preoperative PSA value to decline to normal following prostate resection is strong indirect evidence of incomplete resection or disseminated disease. Serial PSA determinations allow the clinician to assess the progress of the patient with disseminated disease receiving systemic therapy.