Role of serum prostate-specific antigen as predictor for bone metastases in newly diagnosed prostate cancer

Prostate cancer is most frequently diagnosed cancer of men and bone is the most common site of metastasis. There is a lack of consensus for the selection criteria for bone scan in low-risk patients. Western guidelines do not recommend use of bone scan in asymptomatic patients and in low prostate-specific antigen (PSA) values. We try to correlate the PSA value with bone metastases through bone scan in the Indian population.

A total of 68 histologically newly diagnosed prostate cancer subjected to bone scan were retrospectively analyzed. The patients were stratified into four groups according to their PSA level: The first group of patients had PSA level ranging from 0 to 10 ng/ml (n = 4), the second group had PSA level ranging from 10.1 to 20 ng/ml (n = 13), the third group had PSA levels 20.1-100 ng/ml (n = 23), and the fourth group has PSA >100 (n = 28).

The incidence of osseous metastases proven by bone scan was found to be zero (0 out of 4) for PSA level 0-10 ng/ml; 38.46% (5 out of 13) for PSA level 10.1-20, 60.87% (14 out of 23) for PSA level 20.1-100 ng/ml, and 100% for PSA >100 (P < 0.005) (95% confidence interval 1.01-1.1). For cut-off value of PSA ≤10 ng/ml, sensitivity and specificity were 100% and 19.05%, respectively, with positive predictive value of 73.44%.

The correlation between PSA value and presence of metastases confirms the usefulness of bone scan scintigraphy in prostate cancer staging. The screening bone scan at initial diagnosis should be included for all patients with PSA >10 ng/ml in Indian setting.