Multiparametric MRI (mpMRI) has sparked a revolution in prostate cancer (PCa) detection, diagnosis and image-guided treatments. Transrectal ultrasound (TRUS) does not even begin to compare with the anatomic definition and tissue characterization provided by high-resolution, 3D mpMRI scans. This breakthrough technology has been a godsend for patients in such areas as

• Avoiding unnecessary needle biopsies
• Guiding targeted biopsies for maximum diagnostic accuracy with minimal needles
• Confirming and monitoring candidates for Active Surveillance (AS)
• Guiding minimal-to-noninvasive focal therapy such as our Focal Laser Ablation (FLA).

With advantages like these, more patients (and their urologists) are relying on the valuable information gained from mpMRI, which particularly excels in identifying significant disease that is potentially lethal, unlike insignificant disease that qualifies for AS or focal therapy. In fact, one of the few criticisms regarding mpMRI is that it may not detect and reveal small tumors.

Missing small tumors – is that a big problem?

University College London is fortunate to have one of the most globally respected “brain trusts” in PCa. Among its members and affiliates are two imaging/prostate cancer experts, Drs. Mark Emberton and Hashim Ahmed. They and their colleagues have designed and conducted some of the most important research studies, and have been ahead of the curve in terms of understanding the nature of both significant and insignificant PCa.

They and 23 other authorities/researchers tackled a key question: Knowing that mpMRI may not pick up small tumors, how can we discover the attributes of these tumors? Or, I would put it like this: if mpMRI overlooks small tumors, is the patient living with an unknown danger?

I was happy to read a newly published (May, 2020) paper by Ahmed, Emberton and a consortium of British clinicians and scientists, “What Type of Prostate Cancer Is Systematically Overlooked by Multiparametric Magnetic Resonance Imaging? An Analysis from the PROMIS Cohort.”^[i] I have previously written about the PROMIS (Prostate MR Imaging Study) study, which was conducted to determine the performance of mpMRI and TRUS-guided biopsy in detecting significant cancers.

The authors of this reassuring paper utilized the data from the original study, and re-analyzed it using two definitions for significant PCa:

1. Gleason 4+3 or higher of any length or maximum cancer core length of 6 mm or more of any grade
2. Gleason 3+4 or higher of any length or maximum cancer core length of 4 mm or more.

mpMRI results were compared with actual tissue findings (pathology) from 3D transperineal mapping biopsies (TPMs) which take needle “snips” throughout the entire gland at a distance of 5mm apart. Next to using an actual prostatectomy specimen (whole gland removed from the body), the TPM is the most thorough sampling method possible. If a TPM biopsy finds PCa, its exact location, Gleason grade and extent of disease are known, so it’s an excellent way to compare tissue vs. MRI results.

Based on this comparison, the authors found that if mpMRI missed PCa, it had

…significantly lower overall and maximum Gleason scores and shorter [maximum cancer core length] than cancers that were detected (5 vs 8 mm). No tumors with overall Gleason score higher than 3+4 (Gleason Grade Groups 3 to 5) or maximum Gleason score greater than 4+3 (Gleason Grade Groups 4 to 5) on TPM biopsy were undetected by MRI…^[ii]

What does this mean for patients?

The above is good news. It means that tumors that are not detected by mpMRI are smaller and less aggressive than the ones picked up by the scan. More importantly, in this particular study the authors report that none of the most aggressive tumors were overlooked by mpMRI scans. Meanwhile, they will continue their research into the cellular and molecular nature of insignificant and significant PCa, which will shed more light on the exact nature of tumors that are “invisible” to mpMRI.

NOTE: This content is solely for purposes of information and does not substitute for diagnostic or medical advice. Talk to your doctor if you are experiencing pelvic pain, or have any other health concerns or questions of a personal medical nature.

References

[i] Norris JM, Carmona Echeverria C, Bott SRJ, et al. What type of prostate cancer is systematically overlooked by multiparametric magnetic resonance imaging? An analysis from the PROMIS cohort [published online May 1, 2020]. Eur Urol. doi: 10.1016/j.eururo.2020.04.029
[ii] Charnow, Jody. “Study: Prostate Tumors Missed by mpMRI Less Aggressive.” Renal & Urology News, May 8, 2020. https://www.renalandurologynews.com/home/news/urology/prostate-cancer/study-prostate-tumors-missed-by-mpmri-less-aggressive/