whole-body bone scan for detecting bone metastasis in the prostate-specific membrane antigen positron emission tomography era: a retrospective cohort study of post-radical prostatectomy prostate cancer patients

Objective(s): to determine the detection rate of bone metastasis on bone scan of prostate cancer patients with rising serum prostate-specific antigen (psa) following radical prostatectomy (rp) and to identify the predictive factors associated with bone metastasis.methods: a study was conducted in 120 patients with rising serum psa after rp. the data collected were pre and post-rp clinical parameters, including a trigger psa (tpsa) level that prompted the treating physician to request a bone scan and psa doubling time (psadt). bone scans were classified as positive or negative in conjunction with follow-up imaging and clinical information.results: of 120 bone scans, 6 (5%) were positive and 114 (95%) were negative for bone metastasis. in the median tpsa ranges of <0.5, 0.5-1.0, and >1.0 ng/ml, scan positivity was 2.1%, 6.3%, and 30%, respectively. patients with positive scans showed higher tpsa (1.228 vs 0.256 ng/ml; p=0.003) and shorter psadt (3.5 vs 12.2 months; p=0.005) than those with negative scans. the most significant predictors of a positive bone scan were tpsa (>1 vs ≤1 ng/ml; or 15.286, 95% ci 2.594-90.064, p=0.003) and psadt (<6 vs ≥6 months; or 17.333, 95% ci 1.618-185.646, p=0.018).conclusion: the detection rate of bone metastasis on bone scans in post-rp recurrent prostate cancer patients is only 5%, but the probability is much higher with tpsa >1 ng/ml and psadt <6 months. given its wide accessibility in thailand, a bone scan should remain the preferred screening test for bone metastasis, with expected positive results in patients with high or rapidly rising psa levels.