Who really needs a bone scan at time of diagnosis?
Posted Mar 09 2011 12:00am
Every year tens of thousands of men newly diagnosed with prostate cancer are given a bone scan (and other types of scan) as part of their “normal” diagnostic work-up. The only value of the bone scan is that it is able to identify men who already have (or at least may have evidence suggesting) actual metastatic prostate cancer to their bones at the time of diagnosis.
At least two major sets of guidelines today state clearly that bone scans are not necessary in men diagnosed with low- and intermediate-risk prostate cancer:
According to the guidelines issued by the European Association of Urology (EAU), bone scans “may not be indicated in asymptomatic patients” if the PSA level is < 20 ng/ml and the Gleason score is < 8.
Guidance documents available from the National Cancer Institute and the American Urology Association offer no specific commentary on the appropriate use of bone scans as part of the work-up of the newly diagnosed prostate cancer patient.
McArthur et al. have just reported data from a cohort of > 800 patients in whom they sought to ensure the feasibility of implementing the current EAU guidelines (which, to all practical intents and purposes, are precisely the same as the NCCN guidelines on this issue).
Their data are based on newly diagnosed patients identified between March 2005 and January 2010, all of whom received a staging bone scan. However, patients were not eligible for inclusion in the analysis if no Gleason score was available or if their most recent PSA test was taken > 3 months prior to the bone scan.
Here are the findings:
The entire database included 819 patients, of whom 633 were assessed retrospectively and 186 prospectively.
672/819 patients met all the inclusion criteria.
The average (median) age of the eligible patients was 71 years (range, 39 to 93 years).
54/672 eligible patients (8 percent) had evidence of metastasis to bone based on their bone scans.
PSA levels and Gleason scores were both independent predictors of a positive bone scan, and their predictive value was additive.
357/672 patients had a PSA level < 20 ng/ml and a Gleason score < 8 and none of these patients had a positive bone scan.
McArthur et al. very reasonably conclude that a bone scan “can be safely omitted” from the work-up of newly diagnosed prostate cancer patients with a PSA level < 20 ng/ml and a Gleason score < 8.
Of course, legal advisers to the average American urologist might well continue to suggest that a bone scan was a good idea for many men who do in fact meet the criteria specified above. It is the exception that proves the rule, and it is certainly the case that bone metastasis has very occasionally been identified in men with a PSA < 20 ng/ml and a Gleason score of < 8. However, this has less to do with good medical practice and much more to do with protecting the urologist against “malpractice” under such circumstances (which isn’t really malpractice at all).