[When should we perform a bone scintigraphy in patients with new diagnosis of asymptomatic prostate cancer in order to detect bone metastasis?].

Objective: To define, based on PSA value, Gleason score (GS), clinical stage and age, those patients diagnosed with asymptomatic prostate cancer whose cases warrant further study of bone metastasis (BMet).

Methods: From January 2006 to May 2010, we evaluated 263 patients diagnosed with prostate cancer who were chosen for further study of bone scintigraphy following the consensus protocol accepted by the Ministry of Health of Andalusia (Integrated Andalusian Process Prostate Cancer-BPH). All selected studies met the criteria defined in the test indications: PSA >10 or Gleason score (GS) ≥7 or positive biopsy of seminal vesicles, all without symptoms of bone pain. A multivariate analysis of potential predictive factors for positive bone scintigraphy was performed and cutoffs were determined by calculating the following diagnostic rates: sensitivity, specificity and positive and negative predictive values with their respective confidence intervals at 95% certainty.

Results: BMet were detected in 29 cases (11%). The average age of the patients with a positive bone scan was 65.5 and 68.4 years in those with a negative result (p=0.03). Multivariate analysis showed that GS OR: 2.08 [95% CI (1.34 - 3.18)] (p<0.001) and PSA level 21-200 ng/ml OR: 3.68 [95% CI (1.13-1.02)] (p<0.05) were independent predictive variables for positive bone scan. The cutoffs were estimated by ROC curve analysis, resulting in a cutoff of 16.18 ng/ml for PSA value and 7 for GS (larger area under the curve: 0.864 with a sensitivity of 94.5% and specificity of 47%).

Conclusions: In the group of patients defined in our study, diagnosed with asymptomatic prostate cancer, the assessment of BMet using a bone scan should be carried out with a PSA level ≥ 16.18 ng/ml and GS ≥7 as reference points.