Procollagen type I carboxyterminal extension peptide in serum: a reliable marker of bone metastatic disease in newly diagnosed prostate cancer?

Objective: This study evaluates the accuracy of type I procollagen, a bone matrix glycoprotein, and prostate-specific antigen (PSA) as markers for predicting the results of radionuclide bone scan in newly diagnosed, previously untreated patients with prostate cancer.

Methods: 74 patients underwent serum PSA and procollagen determination using specific antibodies. A staging radionuclide bone scan was then performed; patients with positive bone scan were submitted to x-rays of the suspicious zones. Then, we calculated sensitivity, specificity, positive predictive value, negative predictive value and overall accuracy of procollagen and PSA in the detection of bone metastases.

Results: Procollagen alone had 83.3% sensitivity, 96% specificity, 90.9% positive predictive value, 92.3% negative predictive value and 91.9% overall accuracy. PSA alone had 70.1% sensitivity, 86% specificity, 70.8% positive predictive value, 86% negative predictive value and 81.1% overall accuracy.

Conclusions: According to our data, we no longer perform a staging radionuclide bone scan in patients with PSA < 20 ng/ml and normal procollagen level, diminishing the number of radionuclide bone scans and increasing the overall net savings for the health care system.