Broadening the criteria for avoiding staging bone scans in prostate cancer: a retrospective study of patients at the Royal Marsden Hospital

To determine if it is possible to exclude staging bone scans in a greater proportion of patients if more consideration is given to T stage and Gleason score, as recent guidelines from the National Institute of Clinical Excellence state that routine staging bone scans for prostate cancer are unnecessary in patients with a prostate specific antigen level (PSA) of < 10 ng/mL and Gleason scores of < 8. We identified a cohort of consecutive patients with untreated prostate cancer who had a staging isotope bone scan between 1 January 1995 and 31 December 2000, who were not on hormone therapy, who had their PSA estimated within 30 days of the scan, and who had histologically confirmed prostate cancer on biopsy reviewed at the Royal Marsden. Data were analysed according to Gleason score, major Gleason grade, clinical T-stage and PSA level. In all, 420 patients were identified who fulfilled the criteria for inclusion; 67 scans (16%, 95% confidence interval, CI, 13-20%) were positive. Of the 187 scans taken in patients with a PSA level of less than or equal to 20 ng/mL, stage < T4 and Gleason < 8 (with major Gleason grade < 4), two (1%, 0.3-4%) were reported as positive, giving a negative predictive value of 99% (95% CI 98.5-99.5%) for these criteria for avoiding the need for staging bone scans. In 116 patients (28%) with Gleason score 7, of whom 28 (24%) had positive scans, there was a statistically significant association between positive scans and a major Gleason pattern of 4 compared with 3. Isotope bone scans are an unnecessary part of staging of prostate cancer if the PSA level is less than or equal to 20 ng/mL, stage < T4 and Gleason score < 8, and should be omitted unless the major Gleason pattern is 4. The present results suggest that by considering the Gleason score and T stage, a larger proportion of patients with prostate cancer than previously thought could avoid a staging bone scan.