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Over- and under-imaging of newly diagnosed prostate cancer patients

Posted Feb 20 2011 12:00am

This is hardly a radical new finding but yet another study has recently shown that we are over-using expensive scanning tests in the work-up of patients diagnosed with low- and intermediate-risk prostate cancer and under-using these tests in men initially diagnosed with high-risk disease.

Prasad et al. have reported, based on a retrospective analysis of data from the SEER-Medicare database, that during 2004 and 2005:

  • 36 percent of 9,640 men diagnosed with low-risk prostate cancer
  • 49 percent of 12,966 men diagnosed with intermediate-risk prostate cancer
  • 39 percent of 7,577 men diagnosed with high-risk prostate cancer

were being given bone scans, magnetic resonance imaging (MRI), computer-assisted tomography (CT), or positron emission tomography (PET) imaging studies.

As Prasad et al. point out, what this really means is that perhaps a third of all patients being diagnosed with very low-, low-, and intermediate-risk prostate cancer are being subjected to high-tech imaging studies that are almost certain to be negative, whereas about a third of the men who probably should be getting such scans (among the high-risk patients) are not getting them.

There are all sorts of possible reasons to explain these findings … some fractionally more ”reasonable” than others … but the bottom line is almost certainly that two things are driving most of the over-use of such imaging tests in the low- and intermediate-risk patients: fear of malpractice law suits and patient demand. It is much harder to explain why such tests are being under-used in the high-risk patients.

In an era when cost-effectiveness is starting to become a real issue, Prasad et al. estimate that the total annual cost of such unneeded testing is about $35 million every year in prostate cancer alone … which equates to about 10 percent of what the National Cancer Institute spends each year on prostate cancer research. Most of that money is being spent on PET scans, which are of very limited proven value in the management of prostate cancer to date, however technologically “cool.”

Clearly there are some individuals for whom high-tech scans may be appropriate even though they appear to have low- or intermediate-risk prostate cancer.

Imagine, for example, a man with a clearly positive DRE in the left lobe of the prostate. His biopsy shows Gleason 7 disease in three cores but these are all in the right lobe, and his PSA is 9.2 ng/ml; up from 3.8 ng/ml two years earlier, when a first biopsy was negative. Carrying out an MRI and a CT scan on such a patient might be wise just in case it is possible to identify whether there really might be Gleason 7 to 10 cancer in the left lobe that was “missed” by the biopsy. After all, this man has gone from having no apparently serious indicators of prostate cancer in 2009 to clinically significant risk in early 2011. But a case like this is relatively unusual in the grand scheme of things. Use of such scanning techniques is probably actually justifiable in, at most, 1 percent of men initially diagnosed with low- and intermediate-risk prostate cancer.

It was particularly interesting to note that the use of such scanning techniques was most common among who went on  to receive treatment with external beam radiation therapy and/or brachytherapy (at 46 percent in the low-risk patients, and 61 percent in the intermediate-risk patients). By comparison, the lowest use of high-tech imaging was among men who subsequently elected to have watchful waiting (at 14 percent in the low-risk patients, and 18 percent in the intermediate-risk patients).

Prasad et al. were also able to show that the use of high-tech imaging was more common in men who were older than 75 years, black, relatively wealthy, or lived in rural regions. In contrast it was less likely to occur in men who were well educated.

What should we make of all this? Well … with carefully selected exceptions we are probably wasting vast amounts of money each year that could be applied with greater benefit to research into prostate cancer. Think hard about whether it is really necessary when your physician starts ushering you to the MRI machine or the PET scan and make sure you ask him whether the results of such a scan are really likely to make any change to what he is expecting to see or what he is expecting to do if you ask him to treat you.

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