Appropriate frequency of spinal MRI scans in men with metastatic CRPC

Spinal cord compression (SCC) is a major complication of metastatic castration-resistant prostate cancer (CRPC) and the onset of SCC is associated with potentially severe neurological problems. Targeted radiotherapy can be used to delay or prevent the progression of SCC, but is most effective when SCC are detected as early as reasonably possible.

Venkitaraman et al. have attempted to determine the optimal frequency of spinal magnetic resonance imaging (MRI) to detect SCC by analyzing clinical data from 130 consecutive patients with CRPC. These patients had no functional neurological deficit, and all received spinal MRIs between January 2001 and May 2005. Patients found to have SCC were treated with radiotherapy. All patients were followed to document the incidence of neurological deficit.

The results of this study showed the following:

  • 37/130 patients (28.4 percent)  had SCC on MRI.
  • The number of patients with SCC and free from neurological deficit gradually declined: from 94 percent at 3 months to 43 percent at 24 months.
  • The number of patients without SCC and free from neurological deficit also declined over the same timeframe: from 97.5 percent) to  63 percent at 24 months.
  • The only independent predictive factor of future neurological deficit was a PSA doubling time < 3 months.

The authors conclude that spinal MRIs can be used to detect asymptomatic SCC in patients with CRPC. They further note that serial MRIs are required to maintain a low incidence of clinical SCC and that the optimum frequency of the MRIs depends on the subset of patients studied. They suggest, based on the results of their study, that the optimal frequency for spinal MRIs would be every 4-6 months for CRPC patients with previous SCC, rapid or high PSA or back pain and annually for patients with CRPC but no symptoms suggestive of SCC.

2 Responses

  1. Did Dr. Venkitaraman have a financial interest in the MRI?

    Where was the control group?

    This is not science.

  2. Dear Dr. Kelly:

    Since Dr. Venkitaraman and his colleagues are all in the UK, I think we can say with some certainty that they had no financial interest in the MRI (which would be owned by their regional health authority).

    I don’t think that anyone is suggesting that this was a randomized, double-blind, controlled trial. It is retrospective data analysis. The “control group” is the set of patients that did not show SCC on MRI, and who certainly appear to be at lower risk for SCC over time. Would I like to see this study repeated in a randomized manner with patients followed for the remainder of their lives, and a control group that received no MRIs at all? Sure, that would provide us with category 1 evidence. Do I think this study will be done? No, probably not because of the costs involved. However, as I am sure you are aware, a vast proportion of clinical practice must be carried out without the benefit of category 1 evidence, that’s why medicine is as much an art as a science!

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