Limited predictive accuracy of endorectal coil MRI

Patients believed to be at potential risk for prostate cancer that may extend outside the prostate itself — through extracapsular extension (ECE) or seminal vesicle invasion (SVI) — often undergo imaging studies in planning for their treatment. Endorectal coil magnetic resonance imaging (erMRI) as been a commonly used form of such imaging.

Brajtbord et al. have reported data from a series of 1,161 robotic-assisted laparoscopic prostatectomies (RALPs) performed by a single surgeon. The database was used to identify patients who were given an erMRI before RALP in an attempt to assess the predictive accuracy of erMRI as a means to identify the presence of absence of ECE or SVI prior to surgery when compared to the patients’ pathological outcomes post-surgery. The database included patients who received their erMRIs at academic and non-academic centers.

The results of this analysis are reported as follows:

  • 179/1,161 patients in the series (15.4 percent) had received an erMRI prior to RALP.
  • The 179 patients who underwent erMRI had significantly worse disease  than the 982 patients who did not have an erMRI.
  • Among 110 patients with pathologically organ-confined (pT2) disease post-surgery
    • 81 (74 percent) were correctly diagnosed as organ-confined on erMRI.
    • 29 (26 percent) were inaccurately diagnosed as having cT3 disease (false positives).
  • Among 69 patients with pT3 disease post-surgery
    • 30 (43 percent) were correctly diagnosed as having cT3 disease on erMRI.
    • 39 (57 percent) were inaccurately diagnosed as having cT2 disease (false negatives).
  • The overall sensitivity and specificity of erMRI for diagnosis of pT3 disease were 43 and 73 percent, respectively.
  • When stratified by pathological stage (pT3a or pT3b)
    • The sensitivity and specificity of erMRI to accurately diagnose ECE are 33 and 81 percent, respectively.
    • The sensitivity and specificity of erMRI to accurately diagnose SVI are 33 and 89 percent respectively.
  • The positive predictive value of erMRI to assess the presence of ECE and SVI is 50 percent for both clinical conditions.
  • The negative predictive values of erMRI to assess the absence of ECE and SVI are 61 and 63 percent, respectively.
  • erMRIs performed at academic centers had similar rates of sensitivity (at 67 vs 77 percent) and specificity (at 39 vs 54 percent) compared to those performed at non-academic centers.

The authors conclude that — on the basis of current practice patterns in the USA — erMRI has limited clinical value in the preoperative detection of ECE and SVI. They also conclude that the accuracy of detection of T3 disease did not improve at academic centers or among high-risk patients.

These data are not exactly compelling evidence for the value of erMRI in the assessment of the clinical stage of a patient’s prostate cancer prior to treatment.

2 Responses

  1. The study doesn’t indicate if the MRI was a Telsa 1.5 or a Telsa 3 MRI. I would imagine that a Telsa 3 MRI would give a superior outcome.

  2. The full paper may give more detailed information, but … Since 3.0 T erMRI has been a comparatively recent development and is still not widely available at this time, my guess would be that most of these patients would have received 1.5 T erMRI.

    Much as one would like to believe that 3.0 T erMRI would give more accurate results, it would be unwise to make such a decision without good data to support it.

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