“In the 100 years from the mid-15th to the mid-16th century, a combination of circumstances stimulated men to seek new routes, and it was new routes rather than new lands that filled the minds of kings and commoners, scholars and seamen.”– Encyclopedia Britannica
When the 15th century launched the Age of Discovery, it was actually common knowledge that the earth is round. The competition for alternatives to overland routes for the Asian spice trade fostered the latest European shipbuilding designs and compelled heading into uncharted waters. When Columbus set sail in 1492, he navigated using the time-honored compass-based method called dead reckoning, since the superior accuracy of celestial navigation was still in research and development by the Portuguese.
In the world of prostate cancer (PCa), we too are now in an Age of Discovery. Just as celestial navigation gradually replaced cumbersome dead reckoning, multiparametric MRI is increasingly replacing the relatively cumbersome way of gaining prostate information using transrectal ultrasound (TRUS) imaging. In writing about this revolution, Connor, et al. (2020) call it “the era of routine multiparametric MRI,” and discuss how mpMRI has fostered focal therapy as an alternative route for treating PCa.[i]
Why did it take so long to develop focal therapy?
For the past five decades, the goal of PCa treatment was to eradicate the cancer by radically obliterating the entire gland. Why the whole gland? Well, PCa was assumed to be a multi-focal disease that microscopically permeated the whole prostate in addition to known solid tumor(s). Therefore, radical prostatectomy (surgical gland removal) and whole gland beam radiation or seed implants (brachytherapy) were the only potentially curative options for localized prostate cancer.
This multi-focal assumption prevailed was because there wasn’t sufficient technological development to demonstrate otherwise. Ultrasound can’t distinguish healthy tissue from cancerous tissue, and TRUS biopsy is subject to the dual flaws of over-detecting insignificant PCa and under-detecting significant PCa. If you can’t have reliable information on the true size, shape, location, and aggression level of a patient’s disease, common sense dictates good riddance to the prostate along with the PCa it contains.
Routine mpMRI revolutionizes the PCa world
According to the Connor paper, mpMRI has had three major impacts that revolutionize the PCa world:
- Improving the diagnosis-to-treatment pathway
- Identifying candidates for focal therapy
- Providing accurate guidance for effective focal treatment.
First, mpMRI has altered the traditional diagnostic pathway consisting of elevated PSA/abnormal DRE leading to 12+ needle TRUS biopsy leading to aggressive whole gland treatment. As mpMRI is becoming the “new normal,” the alternative pathway consists of elevated PSA/abnormal DRE leading to mpMRI, leading to a decision if biopsy is required, leading to minimal needle MRI-guided targeted biopsy if needed, leading to tailored treatment options. The obvious advantages of the alternative route include avoiding unnecessary biopsies, and matching treatment to disease.
Second, using the alternative mpMRI pathway allows the identification of men whose PCa is qualified for a focal treatment such as Focal Laser Ablation. In its early days, the initial lack of focal therapy cancer control data resulted in skepticism among urologists that focal therapy was in a patient’s best interest, but they could not deny that preserving urinary and sexual quality of life was excellent with focal treatment and that a growing number of qualified patients were asking for it. We now have published data that cancer control for focal therapy and robotic prostatectomy are roughly equal at 5 years.
Third, thanks to mpMRI’s remarkably accurate 3-D portrait of prostate anatomy and any significant PCa it may contain, focal therapy can be pinpointed onto the target, monitored during treatment, and confirmed immediately after. As the Connor article says, “Success is principally dependent on highly accurate patient selection and disease localization underpinned in large part by the routine integration of pre-biopsy mpMRI. Prospective medium-term follow-up data for primary HIFU and cryotherapy for men with intermediate-risk disease have shown acceptable cancer control with low risk of side effects and complications.”
Improving over time
We know from the ship’s log that Columbus kept during his first voyage that he stuck to a westward heading for weeks at a time, thanks to his compass. However, three times he went off course, once due to wind changes and twice due to false signs of land toward the southwest. Fortunately, hitting the western hemisphere was inevitable; unfortunately, not knowing the size of the globe, it wasn’t Asia. He did try using the newer celestial navigation devices 5 times but none succeeded, “… sometimes because of bad luck, and sometimes because of Columbus’s own ignorance of celestial tools.”[ii]
The earliest adopters of focal PCa treatment using cryotherapy (freezing) were very much like Columbus. Their navigation methods into the prostate gland to locate the tumor and successfully encompass it with ice were guided by TRUS—sort of like dead reckoning—because they didn’t yet have MRI. Navigating by stars eventually led to more accurate routes; now our mpMRI guides us accurately to today’s PCa goals.
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] Connor MJ, Gorin MA, Ahmed HU, Nigam R. Focal therapy for localized prostate cancer in the era of routine multi-parametric MRI. Prostate Cancer Prostatic Dis. 2020 Feb 12. doi: 10.1038/s41391-020-0206-6