Prostate Cancer Treatment (Professional) (cont.)
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Stage Information for Prostate Cancer
Detection of asymptomatic metastatic disease in prostate cancer is greatly affected by the staging tests performed. Radionuclide bone scans are currently the most widely used tests for metastases to the bone, which is the most common site of distant tumor spread. Magnetic resonance imaging (MRI) is more sensitive than radionuclide bone scans but is impractical for evaluating the entire skeletal system. Some evidence suggests that serum prostate-specific antigen (PSA) levels can predict the results of radionuclide bone scan in newly diagnosed patients. In one series, only 2 of 852 patients (0.23%) with a PSA of less than 20 µg/L had a positive bone scan in the absence of bone pain. In another series of 265 prostate cancer patients, 0 of 23 patients with a PSA of less than 4 µg/L had a positive bone scan, and 2 of 114 patients with a PSA of less than 10 µg/L had a positive bone scan. Prognosis is worse in patients with pelvic lymph node involvement.
Whether to subject all patients to a pelvic lymph node dissection (PLND) is debatable, but in patients undergoing a radical retropubic prostatectomy, the nodal status is ascertained as a matter of course. In patients who are undergoing a radical perineal prostatectomy in whom the PSA value is less than 20 and the Gleason sum is low, however, evidence is mounting that a PLND is probably unnecessary, especially in patients whose malignancy was not palpable but detected on ultrasound.[3,4] A PLND remains the most accurate method to assess metastases to pelvic nodes, and laparoscopic PLND has been shown to accurately assess pelvic nodes as effectively as an open procedure. The exact role of PLND in diagnosis and subsequent treatment is being evaluated, though it has already been determined that the length of hospital stay following laparoscopic PLND is shorter than that following an open procedure. The determining factor when deciding if any type of PLND is indicated is whether definitive therapy may be altered. Likewise, preoperative seminal vesicle biopsy may be useful in patients with palpable nodules who are being considered for radical prostatectomy (unless they have a low Gleason score) because seminal vesicle involvement could affect choice of primary therapy and predicts for pelvic lymph node metastasis.
In patients with clinically localized (stage I or stage II) prostate cancer, Gleason pathologic grade and enzymatic serum prostatic acid phosphatase values (even within normal range) predict the likelihood of capsular penetration, seminal vesicle invasion, or regional lymph node involvement. Analysis of a series of 166 patients with clinical stage I and stage II prostate cancer undergoing radical prostatectomy revealed an association between Gleason biopsy score and the risk of lymph node metastasis found at surgery. The risks of node metastasis for patients grouped according to their Gleason biopsy score was 2%, 13%, and 23% for Gleason scores of 5, 6, and 8, respectively.
Transrectal ultrasound (TRUS) may facilitate diagnosis by directing needle biopsy; however, ultrasound is operator dependent and does not assess lymph node size. Moreover, a prospective multi-institutional study of preoperative TRUS in men with clinically localized prostate cancer felt to be eligible for radical prostatectomy showed that TRUS was no better than digital rectal examination in predicting extracapsular tumor extension or seminal vesicle involvement. Computed tomography (CT) can detect grossly enlarged nodes but poorly defines intraprostatic features; therefore, it is not reliable for the staging of pelvic node disease when compared to surgical staging. Although MRI has been used to detect extracapsular extension of prostate cancer, a positive-predictive value of about 70% and considerable interobserver variation are problems that make its routine use in staging uncertain. Ultrasound and MRI, however, can reduce clinical understaging and thereby improve patient selection for local therapy. Preliminary data with the endorectal MRI coil for prostate imaging report the highest sensitivity and specificity for identification of organ-confined and extracapsular disease.[3,12,13] MRI is a poor tool for evaluating nodal disease.
Two systems are in common use for the staging of prostate cancer. The Jewett system (stages A through D) was described in 1975 and has since been modified. In 1997, the American Joint Committee on Cancer (AJCC) and the International Union Against Cancer adopted a revised tumor, nodes, metastasis (TNM) system that employs the same broad T stage categories as the Jewett system but includes subcategories of T stage, such as a stage to describe patients diagnosed through PSA screening. This revised TNM system is clinically useful and more precisely stratifies newly diagnosed patients. The AJCC further revised the TNM classification system in 2002 and, most recently, in 2010. Both staging systems are shown below, and both are used in this summary to discuss treatment options. A thorough review of the controversies of staging in prostate cancer has been published.
Definitions of TNM
The AJCC has designated staging by TNM classification to define prostate cancer.
Table 1. Primary Tumor (T)a
Table 2. Pathologic (pT)a,b
Table 3. Regional Lymph Nodes (N)a
Table 4. Distant Metastasis (M)a,b
Table 5. Anatomic Stage/Prognostic Groupsab
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