Correlation between Low Gleason Score and Prostate Specific Antigen Levels with Incidence of Bone Metastases in Prostate Cancer Patients: When to Omit Bone Scans?

Background: To identify correlation and incidence of bone metastases in prostate cancer patient with low Gleason scores (GS) and prostate specific antigen (PSA) levels. Materials and Methods: This descriptive restrospective study covered patients with prostate cancer in Cipto Mangunkusumo Hospital in 2006-2011. Of a total of 478, those who had PSA values, histological examination, and bone scan were included, resulting in 358 eligible cases. PSA values were measured using the sandwich electrochemiluminescent immunoassay. Histological examination was graded according to Gleason's grading system and divided into 3 categories: well differentiated ($GS{\leq}6$), moderately differentiated (GS 7) and poorly differentiated (GS 8-10). Bone scans were performed using a radiopharmaceutical agent ($T_c$ 99m methylenen diphosphonate) with images captured by gamma camera. Results: The mean age was $67.5{\pm}7.8$, mean GS was $7.7{\pm}1.3$ and median PSA was 56.9 (range: 0.48-17000 ng/mL). There were 11 patients (3.0%) with positive bone scan with PSA<20 ng/mL and GS<8. Furthermore, there were 2 patients (0.6%) with $GS{\leq}6$ and PSA<10 ng/mL showing bone metastasis. Conclusions: In our study, there were still small percentage of patients with bone metastasis even when low values of PSA (PSA<10 ng/mL) and GS ($GS{\leq}6$) were applied.