We like to believe we are creatures of logic, and that we make rational decisions based on tangible evidence. However, we rarely have an upfront, 100% ironclad guarantee that a choice we’re about to make has the result we most hope for. In such cases, we trust as much evidence as we were able to gather, and hope that as time goes by, our trust will prove justified.

This is often the case in treatment choices for prostate cancer (PCa). In today’s PCa treatment landscape, there is no “silver bullet” that a) works for everyone and b) assures a cure. Even prostatectomy, in which the entire gland is removed, has recurrence rates of roughly 20%. Therefore, all treatments require lifelong monitoring. The question is, how soon should monitoring begin, and what method is best?

Monitoring after radiation

Radiation, whether external beam or seed implants, requires patience to find out how well it has worked. You see, radiation does not instantly kill PCa cells, so the treatment effect is initially invisible. Since PCa cells are less hardy than healthy cells, radiation keeps toxic pressure on their DNA over time. They gradually become unable to reproduce and slowly die off. As it’s occurring, radiation also causes some degree of change in the healthy cells and prostate anatomy, so follow-up imaging usually isn’t done because of the variations and scarring that is happening.

Instead, periodic blood tests are used to see if PSA is coming down. It can take up to 18 months for the PSA to arrive at its lowest point, or nadir, where it is then expected to remain. As months and years go by with no rise after nadir, patients can breathe more easily. Meanwhile, they trust the evidence that radiation has success rates that average 75%–which they hope will apply in their own case.

Monitoring after ablation

MRI-guided ablation, on the other hand, causes a visible effect during treatment itself. This is due to the immediate tissue destruction caused by applying extreme heat or cold. Over the next few months, adjacent healthy tissue heals while the ablation zone forms a type of scar tissue. This effect has distinct characteristics that are identified using multiparametric MRI (mpMRI). As a result, all MRI-guided ablation methods (Focal Laser Ablation, HIFU, TULSA-PRO, cryotherapy, Exablate MRgFUS) can be tracked at regular intervals with the same mpMRI that we use to detect significant PCa.

TULSA-PRO is one of the newer kids on the ablation block, and while there’s not yet mid-to-long term data, many patients like the idea of approach that uniquely applies HIFU via the urethra. Since the ultrasound waves are aimed at the tumor from within the gland, treatment can be planned, mapped, and guided by mpMRI in real time. The tissue destruction area generated by focused ultrasound heat is clearly visible with special real-time MRI software. Immediately after, the ablation zone is confirmed. As with all prostate cancer treatment, success is determined down the road by the absence of new or recurrent cancer. This is where occasional MRI monitoring plays a key role along with PSA.

MRI tracks TULSA-PRO success

Since TULSA-PRO is relatively recent, an April, 2023 published study by a team of German authors reports how they used MRI to monitor tumor response with 19 TULSA-PRO patients.^[i]

After treatment, patients were monitored on a powerful 3T magnet (such as we use) at 1, 3, and 6-12 months. The team found that mpMRI earlier than 6 months was inconclusive because the treatment zone and surrounding area were still resolving, creating confounding artifacts. Therefore, they recommend waiting 6-12 months post-treatment to begin tracking.

They particularly point to Diffusion-Weighted Imaging (DWI-MRI) as the scanning sequence that best distinguishes among healthy, BPH or cancerous prostate tissue based on the motion of water molecules. Since PCa creates abnormally dense tissue, it restricts molecular motion, and this can be “measured” as a quantitative value called the Apparent Diffusion Coefficient (ADC). The lower the value, the greater the restriction, and therefore the PCa is present. In fact, very low ADC values indicate higher tumor aggression.

At the Sperling Prostate Center, our 3T mpMRI offers patients the benefits of high resolution, 3-D scans for the detection, diagnosis and image-guided ablation of PCa. We provide the three most advanced MRI-guided treatments: Focal Laser Ablation, Exablate MRI-guided Focused Ultrasound, and TULSA-PRO. We can assist patients who are candidates for focal treatment in matching the technology that best suits their disease and their lifestyle. We are confident that after treatment, patients can rely on us for the most accurate success monitoring, no matter which approach they choose. Contact us for more information.

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] Meyer L, Bohlscheid A, Lemmer O, van de Plas J et al. MR-Guided Transurethral Ultrasound Ablation of Prostate Cancer: Initial Experience of Monitoring Tumor Response by Dynamic Apparent Diffusion Coefficient Measurements at 3.0 T. Urol Int. 2023 Apr 18:1-9.