Focal therapies for cancer have been around for more than two decades and have been accepted treatment options for breast and renal cancers. Gaining acceptance for prostate cancer, however, has been a long-winding road.
While the promise of successfully eradicating the tumor with fewer side effects remains high, results have been mixed, and the only consensus that has been reached regarding focal therapies is that more study is needed. As recently as January 2018 a European Association of Urology position paper concludes that focal therapy for primary localized prostate cancer should remain an investigational treatment.
That may be about to change according to a 2017 review of mpMRI and its implications for focal therapy in the journal Translational Andrology and Urology. With the development and rapid advances in multiparametric MRI, authors James Wysock, MD and Herbert Lepor, MD say the imaging technology is making identification and stratification of prostate cancer better than ever, allowing smarter patient selection, and more accurate targeting of clinically significant tumors.
While technological advances have resulted in development of an array of focal therapies the ability to identify and determine the risk of prostate tumors has lagged. There are currently six focal therapies generally considered for treatment of prostate cancer: cryotherapy, high-intensity focused ultrasound (HIFU), irreversible electroporation (IRE), laser ablation, photodynamic therapy, and brachytherapy.
As diverse as these approaches appear to be, they all share two common objectives, one is to minimize the side effects associated with conventional surgery, the other is to provide a treatment option between active surveillance and radical prostatectomy for patients with low-to-intermediate risk disease.
Drs. Wysock and Lepor of the Department of Urology at NYU Langone Medical Center state that much of the challenge to focal therapy for prostate cancer stems from the multifocal nature of the disease and the difficulty of reliably differentiating aggressive high-risk tumors from low-risk lesions and in localizing and marking the borders of those aggressive sites.
“Focal therapy success relies upon accurate tumor localization, tumor boundary definition, effective ablation targeting with adequate margin control and accurate follow-up protocols to assess oncological control,” they wrote.
They say multi-parametric MRI (mpMRI) has significantly improved both disease localization and risk stratification of cancer detected within the prostate.
Citing the PROMIS trial, which provided the highest level of evidence about the accuracy of mpMRI, showed that clinically significant (Gleason 4 or greater) was identified 93 percent of the time, Wysock and Lepor say that overall results of PROMIS suggest a strong argument for including mpMRI in diagnosing prostate cancer.
They caution that a second critical challenge for focal therapy is delivering the appropriate ablation energy to the mass of the tumor, and that the ability of mpMRI to estimate volume remains to be defined. Nevertheless, they conclude that mpMRI promises to give focal therapy the firm basis it has previously lacked to move from an investigational therapy to a standard treatment option.
“The use of mpMRI thus sets the necessary foundation to begin exploring focal therapy strategies,” they wrote. “Future studies will serve to strengthen these data and provide further definition on the exact role of this imaging in disease management.”
Based largely on PROMIS, Professor Mark Emberton of the University College Hospital in London, along with a team of esteemed colleagues, has proposed a new imaging-based pathway for diagnosis, treatment, and follow-up for prostate cancer that incorporates mpMRI and focal therapy when indicated.
The approach is gaining attention and interest from urologists and SonaCare has developed an infographic of the pathway Emberton has proposed.
Click the button below to obtain your free copy of the infographic.