USING PROSTATE-SPECIFIC ANTIGEN TO ELIMINATE THE STAGING RADIONUCLIDE BONE SCAN

Abstract

Traditionally the radionuclide bone scan has been the cornerstone of prostate cancer staging. Previous widespread use of bone-scan imaging was certainly reasonable, even in the asymptomatic patient, as clinicians had no methodology to predict who would or who would not have osseous metastases. Now, in the era of PSA testing, clinicians do have a timely, cost-effective method to determine those patients who are highly unlikely to have osseous metastases. As evidenced by several clinical studies noted previously, a radionuclide bone scan should not be obtained in staging the asymptomatic, newly diagnosed prostate cancer patient with a serum PSA level less than or equal to 10 ng/mL. Incorporation of clinical stage and tumor grade does not significantly improve the predictive value of PSA. Those patients with bone discomfort, however, should undergo bone imaging, regardless of the serum PSA level. Similarly, the serum PSA level may be used to avoid unnecessary bone-scan imaging in the patient with recurrent prostate cancer following definitive treatment. At this time, we do not have enough clinical information to determine the optimal PSA level that will predict precisely which patients will have osseous metastases. From the above reports, however, and the present authors' clinical experience, it would seem reasonable to avoid bone-scan imaging if the post-radical prostatectomy serum PSA level is not more than 2 ng/mL. No absolute data are available about recurrence after radiation therapy or for men being managed with watchful waiting. In an attempt to clarify this issue, there is currently a clinical study underway at the University of Michigan. This study assesses the minimum serum PSA elevation that necessitates bone imaging in restaging the asymptomatic patient with recurrent prostate cancer after radical surgery or definitive radiation therapy. The radionuclide bone scan continues to be the gold standard for the detection of osseous metastases in prostate cancer. Nevertheless, it is unnecessary in the specific situations outlined above. Serum PSA testing allows the physician to refine the use and application of this imaging study, thus providing an opportunity to eliminate expensive and time-consuming studies that ultimately do not contribute additional information. The national economic impact of doing so is tremendous.