Focal therapy has emerged as a treatment strategy for low-risk prostate cancer that bridges the gap between definitive whole-gland treatments and active surveillance, although long-term data are limited. In this interview, John W. Davis, MD, discusses the advantages and limitations of focal therapy, the ideal candidate, and what current guidelines say about its use. Dr. Davis is professor of urology at the University of Texas MD Anderson Cancer Center, Houston. He was interviewed by Urology Times Editorial Consultant J. Brantley Thrasher, MD, professor of urology at the University of Kansas Medical Center, Kansas City.
Please define focal therapy for prostate cancer in its current format.
I think it’s important look at two different, related concepts. The first, which I think is the most critical, is agreeing on what is focal and what is not. Three strategies have been tested in various forms. One is true lesion-directed therapy, which assumes the patient has a positive MRI and an ablation source will be directed at it, plus or minus a defined margin, and that’s probably going to be surgeon dependent. The other two—hemiablation and “hockey-stick” ablation—are not necessarily historically image guided. There is published experienced with both approaches in patients with a low-volume, unilateral biopsy.
Dr. John Ward of MD Anderson worked on the hockey-stick approach over 10 years ago. He found that by studying radical prostatectomy specimens, if you had a patient with unilateral cancer and wanted to address the dominant and most of the secondary tumors, it was necessary to treat the affected side completely and the anterior contralateral side. You might say that shouldn’t be called focal therapy because it’s subtotal therapy, and that’s a fair criticism. Although I haven’t seen data on it, I would imagine it would affect how much residual PSA you will be measuring when you’re treating 25% versus 75% of a gland.
The second concept where there is less controversy involves seven ablation sources: cryotherapy, high-intensity focused ultrasound (HIFU), laser ablation (which assumes real-time MR monitoring), photodynamic therapy, irreversible electroporation, brachytherapy, and radiofrequency ablation.
When you mention laser ablation, what type of laser are you talking about?
They are not identical to holmium or GreenLight type applications for benign disease. These are termed “laser interstitial thermotherapy” that are either continuous wave or pulsed. The mechanisms are the same—thermal coagulation, vascular damage, and finally, cellular damage.
What are the perceived advantages of focal therapy?
The one that is the least controversial is quality of life. Compared to standard, full-gland treatment with surgery or radiotherapy, patients will have less reduction in sexual function and possibly fewer irritative side effects. That probably applies to the range of focal and subtotal approaches I mentioned. There’s plenty of literature on cryotherapy with hockey stick showing that if you leave one entire posterolateral zone alone, patients will have fairly reasonable maintenance of sexual function.
Obviously patients need to be well-selected candidates in terms of prostate size, lower urinary tract symptoms, and pelvic anatomy. In other words, the selection is similar to that used for brachytherapy.