Bone scans in newly diagnosed patients
June, 2000

Bone scanning in newly diagnosed patients with PSA levels of less than 10 ng/ml is not necessary. In the study above by Huncharek et al, 5 of 195 or 2.6% of patients had abnormal bone scans with PSA levels at diagnosis of less than 20. If we use a cut-off of 15 than only 4 patients with abnormal bone scans would have been found. If we plug the patient’s data into the Partin Tables and find < a 15% risk for nodal involvement for this group of patients being evaluated for bone involvement, then only one patient or 0.5% with a PSA of <15 would be missed if a bone scan was omitted from the workup.

In a study by Chybowski et al¹ the negative predictive value for a positive bone scan given a serum PSA of less than or equal to 20 ng/ml was 99.7%. Only 1 patient of 306 with a PSA of less than or equal to 20 (PSA=18.2) had a positive bone scan. Of the 207 patients with PSA's of less than or equal to 10 ng/ml, none had a positive bone scan and only 1 of 99 with a PSA of greater than 10 and less than or equal to 20 had a positive bone scan. It therefore appears reasonable to forego bone scanning in newly diagnosed, untreated patients with prostate cancer, who have PSA's of less than or equal to 10 ng/ml. In my opinion we can extend this conclusion to PSA levels of < 15 if the Partin nodal prediction is <15%.

It is reasonable to consider prospective studies to evaluate results of bone scans of patients with PSA's of greater than 10 and less than or equal to 20. In such a study, the Partin table for risk of nodal involvement (as shown above) could be used. The optimal cut-off to minimize false-negative results could be obtained.

Oesterling et al² also found the rate of false negative results for an abnormal bone scan to be 0.5% using a PSA cutoff value of 10 ng/ml. In their study 39% of patients newly diagnosed with PC in Olmsted County, Minnesota presented with PSA values of 10 ng/ml or less. If this percentage were applied to 180,000 new patients diagnosed with PC in 1999, the result would be that almost 100,000 patients would present with PSA levels of 10 ng/ml or less.

At an average cost of $600 per bone scan this would result in a savings of $60 million dollars per year. If we apply this approach to the use of pelvic and abdominal CT scans and forego them in the same group of patients the annual savings would total $180 million dollars per year. This approach in the selective use of the bone scan, CT abdomen, CT pelvis or MRI pelvis would not only decrease healthcare costs but would also eliminate unnecessary radiation exposure, diminish inconvenience to the patient, decrease the time for technician scanning and waste of equipment and secondary expenses.

References:

1. Chybowski F, Keller J, Bergstrahl E, et al: Predicting radionuclide bone scan findings in patients with newly diagnosed, untreated prostate cancer; prostate specific antigen is superior to all other clinical parameters. J Urol 145:313-8, 1991.
    
2. Oesterling J, Martin S, Bergstralh E, et al: The use of prostate-specific antigen in staging patients with newly diagnosed prostate cancer. JAMA 269:57-60, 1993.

    

Prostate Cancer Research Institute (PCRI)
 

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