Editorial Comment on: MRI Displays the Prostatic Cancer Anatomy and Improves the Bundles Management Before Robot-Assisted Radical Prostatectomy by Schiavina et al .

During robot-assisted radical prostatectomy (RARP), surgeons aim to optimize oncologic outcome while minimizing trauma to adjacent erectile nerves. These goals are often inversely related (i.e., wider resections provide better oncologic outcomes, but impair postoperative erectile function). Alternatively, aggressive nerve sparing (NS) may increase positive surgical margins (PSMs), which are associated with increased 5-year biochemical failure. ¹

Recently, surgical planning has become even more challenging as reduced prostate-specific antigen (PSA) screening has led to the detection of prostate cancers that are higher volume, multifocal, and at a more advanced stage. ² In this environment, Schiavina et al. attempted to decrease surgical margins and guide appropriate NS by using multiparametric magnetic resonance imaging (mpMRI) before RARP. The authors used two high-volume robotic surgeons and compared their surgical plans before and after mpMRI data in 137 consecutive patients vs 166 patients without mpMRI data during a 6-month period. The authors used the presence of extracapsular extension or PSMs at the neurovascular bundle in final pathology analysis to judge the “appropriateness” of any changes in the surgical plan.

The authors should be recognized for their efforts to complete a complex study and reduce their overall PSMs substantially. The cohort without mpMRI had a PSM rate of 24.1%, which was reduced to 12.4% (p < 0.01) in the group that used mpMRI-based surgical planning. One criticism of the study is a higher overall surgical margin rate of 24% in their control group (composed of 71.1% cT1 cancers) compared with more contemporary series with PSM rates in the teens. ^1,3 However, the study group's patients were higher risk: 40.9% pT3a/pT3b disease and 22.6% Gleason 8–10 in final pathology analysis. When comparing demographics, the mpMRI study group vs non-mpMRI control group had unusually high percentage of cT2 (55.5% vs 28.3%) and cT3 (10.9% vs 0%) disease, respectively. In this large group of cT2 patients, reducing PSM from 24% to 6% is commendable.

Although not routine, the authors blinded the radiologist to any clinical parameters. Some would argue that radiologists needed the clinical parameters to raise the predictive value, whereas others, knowing the high variability and subjective nature of PSA, digital rectal examination, transrectal ultrasonography, or pathologic scoring, value an unbiased opinion based on mpMRI findings alone. Although this is a separate argument beyond the scope of this editorial, by blinding the radiologists to the clinical data, the authors preserved mpMRI as an independent variable, free from clinical bias. Furthermore, if the surgeon weighs the clinical parameters and the radiologist mpMRI impression (which also includes clinical parameters), aren't they really just “double dipping” into the clinical salsa?

The authors neglected to indicate how often the mpMRI identified an index tumor focus and whether that correlated with the biopsy or clinical examination and whether a new finding on MRI identified an additional lesion of higher grade that altered the degree of NS or change the primary site of concern to the opposite side of the prostate. Patel et al. previously demonstrated that MRI location of the index tumor focus correlated with the site of the PSM in 70% of men, but were unable to show a significant improvement in their PSM with this knowledge. ⁴

Interestingly enough, the authors reported that mpMRI altered their NS plan in 46.7% of cases. Intuitively, one would naturally assume that the authors simply chose wider resections to decrease PSM; however, mpMRI imaging altered surgeons' plan to more or less degree of NS in near equal directions! In particular, mpMRI resulted in a decrease in unilateral NS, counterintuitively an increase in NS when T3 was clinically suspected, but had little impact when bilateral NS was planned. Their data could be simply summarized as patients who were deemed low risk and bilateral NS planned, mpMRI was unlikely to alter the surgical plan. In patients with a high suspicion for T3 disease, mpMRI may induce a change from non-NS to at least a unilateral NS. The authors evaluated their NS separately and included data on how the MRI changed the degree of NS; however, with no clinical outcome, judging the “appropriateness” or success of NS is difficult without actual clinical outcomes on patient recovery and limits any firm conclusions. Follow-up outcome studies may better answer this important question.

This study examined clinical parameters and mpMRI for preoperative planning, but did not describe intraoperative findings and their effect on NS. Did the team ever change to more or less aggressive NS based on intraoperative findings? Analogous to a quarterback coming to the line with a play, checking the defense, and calling an audible (alternative play), robotic surgery is no different. Surgeons look at all these parameters, weigh them, prioritize them, and develop nomograms, but the experience of what is seen intraoperatively cannot be replaced. Robotics allows observation of paper-thin surgical planes and, as is a fundamental of any surgical training, allows the discovery of natural surgical planes, avoiding and adjusting planes obliterated by invading cancer and improving outcomes with higher case experience. ⁵ For patients, the basic analogy is that when walking down a path overgrown with vegetation, an individual can push these to the side easily, but if they get off the path, the brush becomes thicker and more difficult to pass and they naturally fall back onto the correct path, if they respond to their senses. The study's blind spot is the lack of attention to the impact of the surgeon's intraoperative findings, and it presents an opportunity for further study.

In summary, Schiavina and colleagues used mpMRI to alter their preoperative surgical plan in 46.7% of their patients, which resulted in improved oncologic outcomes. mpMRI may be most useful for cT2 or cT3 suspected disease, wherein a more or less radical approach, respectively, may be employed. Further study is indicated to assess whether these changes will improve long-term oncologic outcomes and improve patient erectile recovery.