Retrospective Study of Predictors of Bone Metastasis in Prostate Cancer Cases

Introduction: The purpose of this study was to identify clinical profiles of patients with low risk of having bonemetastases, for which bone scanning could be safely eliminated. Materials and
Methods: This retrospective crosssectional study looked at prostate cancer patients seen in the Urology Departments in 2 tertiary centres over the11 year period starting from January 2000 to May 2011. Patient demographic data, levels of PSA at diagnosis,Gleason score for the biopsy core, T-staging as well as the lymph node status were recorded and analysed.
Results: 258 men were included. The mean age of those 90 men (34.9%) with bone metastasis was 69.2±7.3 years.. Logistic regression found that PSA level (P=0.000) at diagnosis and patient’s nodal-stage (P=0.02) were theonly two independent variables able to predict the probability of bone metastasis among the newly diagnosedprostate cancer patients. Among thowse with a low PSA level less than 20ng/ml, and less than 10ng/ml, bonemetastasis were detected in 10.3% (12 out of 117) and 9.7% (7 out of 72), respectively. However, by combiningPSA level of 10ng/ml or lower, and nodal negative as the two criteria to predict negative bone scan, a relativelyhigh negative predictive value of 93.8% was obtained. The probability of bone metastasis in prostate cancercan be calculated with this formula: -1.069+0.007(PSA value, ng/ml)+1.021(Nodal status, 0 or 1)=x Probabilityof bone metastasis=2.718x/1+2.718x.
Conclusion: Newly diagnosed prostate cancer patients with a PSA level of10ng/ml or lower and negative nodes have a very low risk of bone metastasis (negative predictive value 93.8%)and therefore bone scans may not be necessary.