IMAGING

Baseline staging of newly diagnosed prostate cancer: a summary of the literature
Abuzallouf S, Dayes I, Lukka H
Kuwait Cancer Control Center, Kuwait City, Kuwait
J Urol. 2004; 171 (6 Pt 1): 2122-7

• Purpose: Staging for prostate cancer often includes bone scanning and computerized tomography (CT). We systematically reviewed the published evidence for these tests.
• Materials and Methods: We searched MedLine for articles on these investigations in newly diagnosed cases of prostate cancer. Data were pooled based on prostate specific antigen (PSA), grade and tumor stage.
• Results: Among 23 studies examining the role of bone scan metastases were detected in 2.3%, 5.3% and 16.2% of patients with PSA levels less than 10, 10.1 to 19.9 and 20 to 49.9 ng/ml, respectively. Scanning detected metastases in 6.4% of men with organ confined cancer and 49.5% with locally advanced disease. Detection rates were 5.6% and 29.9% for Gleason scores 7 or less and 8 or greater, respectively. Among 25 studies CT documented lymphadenopathy in 0 and 1.1% of patients with PSA less than 20 and 20 ng/ml or greater, respectively. CT detection rate was 0.7% and 19.6% in patients with localized and locally advanced disease, respectively. Detection rates in patients with Gleason scores 7 or less and 8 or greater were 1.2% and 12.5%, respectively. These risks were typically much greater on pathological evaluation.
• Conclusions: Patients with low risk prostate cancer are unlikely to have metastatic disease documented by bone scan or CT. Therefore, these investigations should not be standard practice. However, patients with PSA 20 ng/ml or greater, locally advanced disease, or Gleason score 8 or greater are at higher risk for bone metastases and should be considered for bone scan. CT may be useful in patients with locally advanced disease or Gleason score 8 or greater but appears not to be of benefit in patients with increased PSA alone.
  
  
• Editorial Comment
  This is a very useful summary of the literature regarding the value of performing CT and bone scan in patients with newly diagnosed prostate cancer. Although these data is not new, this study clearly emphasizes that these tests should be done only in patients with high risk of presenting nodal or bone metastasis (PSA > 15 or Gleason score above 7 or clinical stage T3-4). In this group of patient, bone scan should be the first test to be done. If negative, CT of the abdomen and pelvis should be the next step. Since lymph node size does not correlate with the presence of metastasis, any abnormal lymph node demonstrated by CT should be further biopsied (CT-guided lymph node biopsy). Previous study has shown that in asymptomatic patients with newly diagnosed prostate cancer and serum PSA levels of less than 20 ng/ml, the likelihood of positive findings on abdominal/pelvic CT is extremely low (< 1%). In the USA, elimination of staging abdominal/pelvic CT in these patients would reduce medical expenditures for prostate cancer management by $20-50 million per year (1). In our opinion, it would be more beneficial to perform an endorectal MR imaging in the group of patients with moderate or high risk of harboring extraprostatic disease. This test is the best one available for adequate local staging of the disease. Endorectal MR imaging of the prostate has remarkable strength in the prediction of extra-prostatic extension of the disease and plays an important role in the evaluation of prostate cancer particularly when evaluated by an uroradiologist (2).

REFERENCES
1. Huncharek MA, Nuscat J: Serum PSA as a predictor of staging abdominal/pelvic CT in newly diagnosed prostate cancer. Abdom Imaging. 1996, 21: 364-7.
2. Wang L, Mullerad M, Chen HN, Eberhardt SC, Kattan MW, Scardino PT, et al.: Prostate cancer: incremental value of endorectal MR imaging findings for prediction of extracapsular extension. Radiology. 2004; 232: 133-9.

Dr. Adilson Prando
Department of Radiology
Vera Cruz Hospital
Campinas, São Paulo, Brazil