A wise art teacher once told her class, “The hardest part of any work of art is deciding when it’s done.” The problem is, how to make that decision? When the artist stands back to see if any finishing touches are needed, it’s a matter of subjective opinion. No two artists will judge completion the same way, so agreed-upon objective “doneness” is impossible. In art, the one who made it gets to say when it’s done.

Focal treatment for prostate cancer (PCa) has some things in common with the art world. For one thing, artists have a variety of tools to accomplish their works: painting, drawing, sculpture, lithographs, photography, etc. Similarly, clinicians have a variety of tools to focally ablate (destroy) tumors within the body: focal laser, TULSA, MRI-guided focused ultrasound, cryotherapy, HIFU, etc.

Likewise, both artists and clinicians need to take a good hard look at their end results to determine if more is needed. The artist steps back to gaze at his creation in hopes that it’s complete. However, since ablation occurs inside the body, the doctor relies on MRI imaging in the months and years after focal therapy for feedback that cancer eradication is complete.

This brings us to a big difference between art and medicine. For the artist, it doesn’t matter if no one else agrees his work is done because ultimately, it’s his own opinion that counts—and when it’s done, it’s done for all time. But for the doctor treating PCa, “doneness” in focal therapy can’t be a matter of personal opinion. Since this approach spares healthy tissue, there is a risk that cancer can come back in the zone of the ablation, or a new cancer can spring up elsewhere in untreated tissue. Ongoing follow-up is necessary, along with an objective, agreed-upon way to evaluate follow-up multiparametric MRI (mpMRI) scans once a patient has had focal therapy.

A new system to score MRI follow-up

This issue has now been addressed by a British team from one of our most esteemed research centers, University College London. Their recently published paper begins by naming the problem: “At present there is no standardised system for scoring the appearance of the prostate on multiparametric magnetic resonance imaging (MRI) after focal ablation for localised prostate cancer.”^[i] In other words, without expert consensus on an objective standard, a clinician’s decision on whether his work is “done” becomes like that of the artist, a matter of personal opinion. This is hardly in the best interest of the patient.

A 5-point scoring system for prostate mpMRI already exists. It’s called PI-RADS (Prostate Imaging Reporting and Data System). It was developed and periodically revised by a panel of global experts. By international agreement, PI-RADS scores indicate the likelihood that PCa is present, where 1 is highly unlikely (very low risk) and 5 is highly likely (very high risk). PI-RADS is used for assessing mpMRI, whether for initial diagnosis and staging, for monitoring during active surveillance, and for possible local recurrence after radical prostatectomy or radiation. However, MRI after ablation is more challenging due to the presence of ablation-related tissue changes such as scarring that can confound interpretation, so PI-RADS standards don’t apply as well for monitoring focal therapy over time.

Thus, there is a need for a dedicated mpMRI scoring system specifically after focal ablation. The authors propose a 3-point scoring system for mpMRI after any method of focal ablation. Their proposed system, called PI-FAB (Prostate Imaging after Focal Ablation), rates the results of each imaging parameter or imaging sequence in this order:

• Dynamic Contrast Enhanced (DCE) sequences
• Diffusion Weighted Imaging (DWI)
• T2 Weighted Imaging (T2-WI)

They note that it’s crucial to compare pre- and post-treatment DCE scans. Other clinical information to take into account is treatment date, ablation method, tumor characteristics such as pretreatment Gleason grade group, greatest cancer core length, PSA, and any PSA movement since treatment.

As with PI-RADS, their new system would provide detailed instructions to assist in analyzing MRI scans and assigning a score for each parameter. An example of PI-FAB application is a post-focal ablation patient who comes for an annual follow-up MRI:

PI-FAB score	Action
PI-FAB 1	Continue monitoring
PI-FAB 2	Assess PSA movement, consider biopsy if PSA is rising, otherwise plan next MRI at 1 year
PI-FAB 3	Recommend biopsy

It is the hope of the authors that their 3-point system will be adopted by clinicians to help them decide on further follow-up. Or, if we can think of focal treatment as a work of scientific art, to equip them with an agreed-upon objective way to know if their work may need any finishing touches.

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] Giganti F, Dickinson L, Orczyk C, Haider A et al. Prostate Imaging after Focal Ablation (PI-FAB): A Proposal for a Scoring System for Multiparametric MRI of the Prostate After Focal Therapy. Eur Urol Oncol. 2023 Dec;6(6):629-634.
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