Abstract:
Objective: To determine the cut-off values for serum Prostate Specific Antigen (PSA) and Gleason score (GS) for predicting bone metastasis of Prostate cancer.
Methodology: 330 Prostate cancer patients were enrolled in the study. PSA and GS were determined using commercially available ELECSYS® assays in the Modular Analytics E170 (Roche Diagnostics) and histopathology respectively. Tc99m methylene diphosphonate (MDP) was used to perform the Bone scans (BS).
Results: BS was positive in 186 (56.4%) patients and negative in 144 (43.6%) patients. Amongst these 186 positive patients, 5 (2.7%) had PSA < 20 ng/ml, and 181 (97.3%) had PSA > 20 ng/ml. Out of the 144 patients with negative BS, 142 (98.6%) had PSA < 20 ng/ml. Only 2 (1.4%) had PSA > 20 ng/ml. In the 147 patients with PSA < 20 ng/ml, 142 (96.6%) did not have metastases. Of the 183 patients with PSA > 20 ng/ml, 181 (98.9%) had positive BS. Using a cut-off value of 20 ng/ml for PSA, 142 scans would have been unnecessary.
Out of the 186 patients with positive BS, 3 (1.6%) patients had GS < 7, and 183 (98.4%) had GS > 7. Out of the 144 patients with negative BS, 84 (58.3%) had GS < 7, and 60 had GS > 7. Of the 87 patients with GS < 7, 3 (3.4%) patients had a positive BS while 84 (96.6%) patients had a negative BS. Of the 243 patients with GS > 7, 183 (75.3%) had a positive BS while 60 (24.7%) patients had a negative GS. This indicates that a GS > 7 cannot be reliably used to rule in the need for a BS in Prostate cancer patients.
Conclusion: Our study concludes that serum PSA < 20 ng/ml can be safely used to omit a BS. It suggests that Gleason Score < 7 nullifies the need to conduct a BS. However, serum PSA is a more reliable indicator of bone metastases because of better sensitivity and specificity.
