On a daily basis—probably far more than we are aware—we choose one thing or another based on how we perceive the information we have. This car is better than that car, this tomato is perfect but that tomato looks damaged, clean-shaven looks good on me but a beard looks bad. As an ancient metaphor puts it, we are constantly separating the sheep from the goats.
And so it is with a new scientific view that prostate cancer (PCa) cells are either insignificant (tame sheep) vs. significant (unruly goats). While definitions of significance/insignificance may differ slightly, experts generally agree that insignificant PCa is safe for Active Surveillance (AS) or focal therapy, thus avoiding whole-gland treatment and its associated urinary/sexual side effects. On the other hand, significant PCa warrants more immediate and aggressive treatment in order to reduce the risk of a potentially dangerous PCa cell line eventually spreading.
How do we detect the difference?
Over the years, I have written numerous blogs about clinical studies showing that multiparametric MRI (mpMRI) has high accuracy rates in detecting significant PCa tumors. For example, in one of my earliest blogs I cited a 2013 study out of the National Cancer Institute that found MRI results correlated strongly with biopsy-proven Gleason 7 PCa. A couple of years later, I wrote about a 2015 multi-center study out of Australia showing a 96% sensitivity rate for mpMRI detection of significant PCa. Many more studies reveal the usefulness and accuracy of mpMRI to identify significant PCa before biopsy, during AS, prior to treatment, and under suspicion of recurrence after treatment. Yes, mpMRI detects significant PCa.
Nonetheless, patients considering AS or a focal treatment for a diagnosed tumor sometimes worry that their mpMRI scan might have missed a small or microscopic cancer that will later prove potentially lethal. I understand their concern that what looks like a tame sheep is actually an unruly goat lurking in their prostate gland. While I can confidently reassure them based on numerous past studies, I am always happy to discover fresh evidence that mpMRI can tell the difference.
The 2020 European Association of Urology Virtual Congress
The global coronavirus/COVID-19 pandemic forced the cancelling of many important medical society conferences that would have met in person, but video communications allowed the global presentation of peer-reviewed studies before member audiences.The 2020 European Association of Urology (EAU)’s Virtual Congress included the following reassuring paper by Norris, et al. (2019).[i]
The analysis done by the authors was based on data from the PROMIS study which involved 576 men who, based on bloodwork or other factors, were suspected of having PCa and had never had a biopsy. For study purposes, all of them had an mpMRI scan, followed by a biopsy procedure that combined a conventional 12-core TRUS biopsy with a transperineal mapping biopsy. Clinically significant PCa was defined in two ways:
- Gleason score ≥ 4+3 of any length or maximum cancer core length ≥ 6mm of any grade, or
- Gleason score ≥ 3+4 of any length or maximum cancer core length ≥ 4mm of any grade.
Key cancer outcomes were compared between men in whom mpMRI detected PCa vs. those for whom mpMRI did not detect PCa.
Here’s the good news from this analysis:
- mpMRI did not miss any significant tumors picked up by the mapping biopsy, according to either definition
- PCa that was not detected by mpMRI was significantly lower in overall Gleason, maximum Gleason scores and shorter maximum cancer core length compared with detected disease.
- When mpMRI results that were negative for PCa were coupled with PSA density (blood test result) at a threshold of > 0.10, the proportion of men with undetected disease to 3% for both definition 1 and definition 2 cancer.[ii]
Compare that last point to inaccuracy rates of TRUS biopsy as high as 30-40% in terms of under-detecting significant PCa.
This is an important study because it can calm patients’ worries that mpMRI has missed a potentially lethal disease. It shows that together with PSA density, mpMRI rarely misses. Just think of the benefits for men who don’t need to have a biopsy, or who can avoid a prostatectomy or weeks of radiation—to name just a few.
In short, mpMRI is a safe, noninvasive and dependable way to have the peace of mind that comes from separating the PCa sheep from the goats.
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.
[i] Norris JM, Echeverria L, Bott SRJ, et al. Which prostate cancers are overlooked by mpMRI? An analysis from PROMIS 2020 European Association of Urology Virtual Congress. July 17-26, 2020.
[ii] Kuznar, Wayne. “Few Significant Prostate Cancers are Undetected by mpMRI.” Urology Times, Jul. 22, 2020. https://www.urologytimes.com/view/68ga-psma-11-pet-imaging-triggers-major-changes-in-management-of-biochemically-recurrent