Does a pre-op MRI change surgical decision-making?

Data presented last week at the annual meeting of the American Roentgen Ray Society suggest that preoperative, endorectal magnetic resonance imaging (eMRI) of the prostate may help urologic surgeons to make decisions about whether to carry out nerve-sparing or non-nerve-sparing surgery in patients with prostate cancer.

Historically, surgeons would decide during an open radical prostatectomy whether to conduct a “nerve-sparing” procedure by sparing one or both of a patient’s neurovascular bundles (NVBs). In making this decision they would largely rely on “haptic feedback” — i.e., what the tissues “felt like.” (The NVBs control a man’s erectile function and also have significant impact on post-surgical continence.)

With the development of robot-assisted laparoscopic prostatectomy (RALP), and the fact that RALP is now the most common surgical technique for the treatment of localized prostate cancers, some surgeons feel that it is more difficult to make the decision whether to spare one or both NVBs during RALP than it was during an open surgical procedure.

McClure et al. therefore wanted to investigate whether preoperative eMRI data changed surgical decisions about the type of operation necessary for each individual patient. Their study was based on data from 104 patients who were initially scheduled to have RALP for the treatment of localized prostate cancer. All patients were scheduled for treatment by a single surgeon.

The results of this study were as follows:

  • 29/104 patients originally scheduled for a RALP had their procedure changed after eMRI data were reviewed by the surgeon.
  • Of the 29 patients for whom the treatment plan was changed
    • 17 (58.6 percent) were changed from non-nerve-sparing to nerve-sparing surgery
    • 12 (41.3 percent) were changed from nerve-sparing to non-nerve sparing surgery.
  • After surgery, 7/104 patients (6.7 percent) were found to have positive surgical margins.
    • 6/7 patients with positive surgical margins (87 percent) were patients with MRI data that had not led to any change in their treatment plan (and who therefore received the originally planned nerve-sparing operation).
    • 1/7 patients with positive surgical margins (13 percent) was a patient with MRI data that had led to a change in his treatment — from non-nerve-sparing to nerve-sparing.
    • There were no cases of positive surgical margins in the patients who were given a non-nerve-sparing procedure.

McClure et al. conclude that a preoperative prostatic eMRI helps the robotic surgeon to optimize nerve-sparing technique without compromising oncologic outcomes in patients receiving a RALP for localized prostate cancer.

The study data available at the present time do not differentiate between patients who had one or both NVBs spared, nor do we have access to the pre- or post-operative clinical stages, Gleason scores, and PSA data for these patients. (We had access only to the abstract of the presentation.)

It is worth noting that this study used 1.5 T MRI and included T2-weighted, diffusion-weighted, dynamic contrast-enhanced imaging, and magnetic contrast spectroscopy. We would assume that 3 T MRI (or higher) would potentially improve the ability to determine who needed non-nerve-sparing surgery. However, the fly in the ointment is that there is no absolute consensus on the clinical significance of positive surgical margins. Obviously, what is of critical importance in avoiding positive surgical margins is the risk of leaving behind prostatic cancer cells that are likely to grow and subsequently metastasize. The hard question for any surgeon is going to be what you say to a patient who is begging you to leave his NVBs intact when you think there is only a very small risk for a positive surgical margin which may be of no real clinical significance.

It would certainly seem that we are moving toward a time when every radical prostatectomy patient should probably receive eMRI prior to surgery as part of a concerted strategy to improve clinical and oncologic outcomes. It is also clear from this study that the surgical treatment of about 25 percent of patients may need to be modified based on eMRI data. The “New” Prostate Cancer InfoLink would like to see at least one large study that confirmed the data presented by McClure et al., but these data do present a strong initial argument in favor of preoperative eMRI — at least for patients undergoing RALP.

One Response

  1. It’s encouraging to see these preliminary results. Hopefully we will see a movement away from routine CT and bone scanning that do little or no good for low-risk patients (per AUA PSA Best Practices Statement of 2009) toward effective imaging that has a real impact on outcome.

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