Purpose: We determined clinical and pathological predictors of positive bone scans and computerized tomography (CT) in patients with biochemical recurrence after radical prostatectomy (RP).
Materials and methods: A retrospective analysis of patients treated with RP at West Los Angeles Veterans Affairs Medical Center and University of California-Los Angeles Medical Center was performed to identify men with biochemical recurrence. All postoperative bone scans and pelvic CT following recurrence and prior to the initiation of hormone ablation therapy were reviewed. Preoperative clinical variables, pathological findings, serum prostate specific antigen (PSA) at postoperative imaging and postoperative PSA doubling time were compared between patients with positive and negative imaging study results.
Results: A total of 128 patients with biochemical recurrence after RP who had postoperative pelvic CT or bone scans available were identified. A total of 97 bone scans were obtained, of which 11 (11%) were positive, and 71 CT scans were obtained, of which 5 (7%) were positive. Men with PSA doubling time less than 6 months were at increased risk of a positive bone scan (26% vs 3%) or positive CT (24% vs 0%) relative to men with longer PSA doubling time. In men with PSA doubling time less than 6 months the risk of a positive study highly depended on PSA at the time of imaging. In men with PSA less than 10 ng/ml the incidence of a positive study was 0% for pelvic CT and 11% for bone scan. In men with PSA greater than 10 ng/ml the risk of a positive study was 57% for pelvic CT and 46% for bone scan. In men with PSA doubling time greater than 6 months no clear relationship to PSA was seen, although the number of patients with a positive study was extremely low (positive bone scans 3% and positive CT 0%). However, none of the 6 imaging studies performed in men with PSA doubling times greater than 6 months and a markedly elevated PSA of 20 to 90 ng/ml was positive.
Conclusions: The risk of detecting metastatic disease by bone scan or pelvic CT in men with biochemical recurrence following RP with PSA doubling time greater than 6 months is low despite marked PSA increases up to 90 ng/ml. In men with PSA doubling time less than 6 months the risk of detecting metastatic disease markedly increases when PSA is greater than 10 ng/ml. These results have important implications for the timing of imaging in patients with biochemical recurrence following RP.