David Crawford, the distinguished Professor of Surgery, Urology, and Radiation Oncology, and Head of the Section of Urologic Oncology, at the University of Colorado Anschutz Medical Campus frames Prostatepedia’s November discussions on focal therapy for prostate cancer.
There is a lot of interest in focal therapy right now. Years ago, when I used to recommend radical prostatectomy and radiation to patients, they would ask why I couldn’t just take out a part of their prostate and not the whole thing. I would chuckle and say, “You can’t do that.” I’d say that prostate cancers tend to be multifocal. We can’t just operate on part of your prostate. We have to treat the whole thing.
That resonated with many urologists for years. Then Drs. Gary Onik and Winston Barzell started using cryotherapy to ablate prostate tumors and mapping biopsies to localize the cancer. Like a lot of things in medicine, there was a backlash of people who felt focal therapy was inappropriate because prostate cancer is multifocal.
Dr. Onik persisted. When somebody came in with a low-grade or even intermediate-grade prostate cancer on the left side of the prostate gland, he would biopsy the right side of the prostate extensively. If there wasn’t any cancer, he would do an ablation and treat the whole left side. That was the beginning of focal therapy.
I became interested in what I call targeted focal therapy about 15 years ago. Of course, focal therapy hinges on our ability to effectively biopsy patients so that you know you’re not missing other, more aggressive tumors. Focal therapy means focally treating a lesion, but I like the term targeted focal therapy because we’re targeting exactly where the tumor is with our mapping biopsies.
There are many ways to do focal therapy. We can use lasers, cryotherapy, or high-intensity focused ultrasound (HIFU). We’re working on using immunotherapy to target lesions. We can even put alcohol into the lesion and get rid of the cancer that way. Ablating the tumor isn’t the hard part. The hard part is knowing where the lesion is and targeting it.
Fifteen years ago, we had several hundred radical prostatectomy specimens; a researcher from Japan named Dasako Hirano, who had been with us for two years, outlined the tumors on acetate paper and then we put them into a 3D system so that we could simulate where these tumors were using different biopsying techniques. We showed that if you use the transperineal approach to place a needle into the prostate every five millimeters, you could sample the whole prostate without missing many significant cancers. I felt that it was safe to go forward with targeted focal therapy.
We knew we would not do any harm with 3D mapping biopsies.
We also talk about MRI in relation to focal therapy. MRI has been around for a long time. We’ve gone from 1 Tesla to 3 Tesla and now 5 Tesla MRI units. We’re getting better at reading the MRI results. There has been a lot of discussion about how accurate MRI is and what it misses. MRIs still can miss aggressive cancers. Depending on which expert you believe, MRI misses anywhere from 7-10% up to 30% of aggressive cancers. MRI is a lot simpler than our painstaking 3D mapping biopsy, though, so it’s caught on.
Dr. Mark Emberton was the first to champion MRI in the United Kingdom. Dr. Emberton and his team now have a lot of experience in using MRI in focal therapy, primarily cryotherapy.
But to me, the gold standard remains the mapping biopsies. MRI is good, but not perfect. Perhaps we can use molecular markers along with MRI to rule out more aggressive cancers.
Focal therapy is a response to overtreatment and it does have a place, but with prostate cancer, we’ve got to follow people a long time before we come to a consensus.