From our perspective at the Sperling Prostate Center, the title question is somewhat absurd. I would respond with, “Who DOESN’T benefit the most from multiparametric MRI of the prostate?” The powerful 3T multiparametric MRI (mpMRI) that we offer provides detection and diagnostic excellence in all of the following scenarios:
- A suspicious PSA and no previous biopsy (do the imaging BEFORE anyone points a biopsy gun at your backside!)
- A suspicious PSA and at least one previous negative biopsy (don’t have another biopsy until you know there’s something there – and then target that area precisely under MRI guidance)
- Obtain information about the aggressiveness of a suspicious lesion seen on mpMRI (use of PI-RADS scoring system)
- A patient who has had a TRUS positive biopsy and appears to be a candidate for Active Surveillance or AS (gain certainty because TRUS often misses significant prostate cancer)
- In combination with PSA blood tests, monitor patients on AS
- Before treatment, use mpMRI results to help prioritize treatment choices, and to plan the treatment itself
- Guidance for focal ablation or hemi-ablation (treating half the gland)
- Monitor focal laser ablation coverage area in real time
- Verify the effectiveness of focal laser ablation immediately following treatment
- Use mpMRI to monitor treatment effectiveness during follow-up – for all radiation and ablation cases
- Use mpMRI to detect possible local or regional recurrence if PSA is rising after any treatment, including surgery, radiation and ablation
Thus, mpMRI has great merit in all prostate cancer scenarios.
However, a new study sheds light on how valuable mpMRI is for a group that many clinicians would assume don’t need imaging: low-risk prostate cancer patients.[i] The goal of the study was to find out if mpMRI offered an additional advantage to the Prostate Cancer Prevention Trial risk calculator (see my blog on how MRI stacks up against other risk calculators). The PCPT risk calculator uses past data from thousands of prostate cancer patients to correlate risk factors with the likelihood of low, intermediate and high risk disease. Perhaps it seems like common sense that those who are predicted to have higher risk disease by the PCPT calculator would benefit the most by undergoing mpMRI to get a clearer picture of what’s going on before choosing a treatment strategy.
Surprisingly, the researchers concluded that for patients with a low risk of Gleason > 7 (less than 10% chance of intermediate risk disease), mpMRI offered the greatest benefit. Why? Because the PCPT risk calculator can’t clearly differentiate between insignificant and significant prostate cancer, a topic under much current discussion. This inherent flaw in risk calculators arises from the inability of TRUS biopsy to adequately interrogate (sample) the whole gland, so it misses significant prostate cancer at least 30% of the time. This throws off statistical predictions because the raw data is inaccurate. On the other hand, mpMRI reveals essential tissue characteristics that define cancer while it creates a 3D portrait of the gland, and excels in detecting even very small foci of significant prostate cancer.
Put another way, if the PCPT risk calculator suggests that a patient is low risk, the best way to verify this is to undergo mpMRI to ensure that no Gleason 7 disease was missed by the biopsy. Think about it: A patient who is told he has Gleason 6 disease and can go on Active Surveillance – when he actually harbors an aggressive cell line – will trustingly pick up his life where he left off while danger is growing in his own body. Even more sobering, since his first TRUS biopsy missed the significant cancer, there is at least a 50% likelihood that it will miss the same location on a repeat biopsy.
To sum it up, I think the study shows us that based on TRUS biopsy combined with risk calculators we simply can’t assume that low risk truly means low risk. Although I disagree that mpMRI offers the “greatest” benefit to these patients over other patients, I certainly want to underscore that mpMRI provides much-needed confirmation for them and their doctors – which indeed has immeasurable value.
[i] Kim EH, Weaver JK, Shetty AS, Vetter JM et al. Magnetic resonance imaging provides added value to the prostate cancer prevention trial risk calculator for patients with estimated risk of high grade prostate cancer less than or equal to 10%. Urology. 2016 Dec 2 [Epub ahead of print]. doi: 10.1016/j.urology.2016.08.074