By: Dan Sperling, MD
A decade ago, focal therapy for prostate cancer was seen as an absurd risk for both doctor and patient. Prostate cancer was held to be multifocal. As early as 1999, a handful of brave physicians were performing focal cryoablation (freezing) at the request of patients so determined to avoid urinary and sexual side effects that they were willing to take the risk of leaving cancer behind. It’s especially astonishing, given that advanced imaging was nonexistent, so focal treatment guided by gray-scale ultrasound was essentially a “shot in the dark”.
We’re come a very long way in 15 years, thanks to pathology evidence revealing that at least 30% of prostate cancer is, in fact, unifocal; additional evidence suggests that even with multiple tumor locations, the index lesion (largest tumor) contains the most dangerous cells. As confidence grew, the annual number of focal cryo cases increased. With hindsight, we can say that the physician and patient pioneers of focal prostate cryo were justified in taking the risk—so much so, that rapid development of more advantageous ablation technologies is occurring, (including HIFU, photodynamic therapy, electroporation, and laser ablation). I offer Focal Laser Ablation because I believe it tops the list.
A snapshot of focal cryo
Because focal prostate cryo has been available since at least 2002, it has the longest and largest statistical record. Thanks to the creation of a multicenter data repository, the COLD Registry, statistics are available on all applications of prostate cryo (total gland, focal, and salvage). A 2011 article in a peer reviewed journal provides the basis for my snapshot of focal cryo.[i] At the time of publication, the COLD registry contained treatment records on 1160 patients identified as having had focal cryo—not every focal cryo case in the U.S., but still a large enough sample on which to base a reasonable analysis. The patients had localized prostate cancer (stage T1c-T2). Enough pretreatment data was available on 1157 of the patients to classify them as low risk (541), moderate risk (473) and high risk (143). In the registry their treatment was labeled as “partial gland ablation.” I’ll come back to that point later.
Focal cryo: what do the numbers show?
As might be expected, since 1999 the number of focal cryo cases increased as the idea of focal treatment became acceptable. The authors compared the results of focal cryo with those of primary whole gland cryo cases (n=4099) in the Registry:
Primary whole gland cryo
|Biochemical disease free (BDF) at 36 months post treatment
|New onset ED (post treatment)
In short, compared with whole gland cryo, focal cryo showed equal cancer control with negligible incontinence and significantly less ED. Still, a 42% rate of new onset ED after focal cryo is hardly ideal. Perhaps this is somewhat explained by the use of the catch-all term “partial gland ablation.” It is not possible from the journal article to analyze the extent of the freeze. How many of these patients had an entire half of the gland frozen (hemiablation) or a half of the gland with a small extension of the iceball into the opposite side (hockey stick ablation), vs a true focal ablation (just the known tumor and a small margin of safety)? Nor does the article specify tumor location; some tumors sit very close to either the external urinary sphincter (very small muscle that controls urination) or the neurovascular bundle responsible for erectile function. The greater the extent of the freeze, the greater the risk of affecting these structures. Therefore, while focal cryo was a tremendous addition to the prostate cancer treatment arsenal, it is no wonder that efforts to improve upon this treatment have engendered new technologies.
3T mpMRI: Beyond focal cryo
Undoubtedly, 3T multiparametric MRI is a game-changer for focal ablation. With its superior ability to produce high resolution images of prostate tumors, we have the ability to gain high-yield biopsies with a minimum number of needles. Utilizing the image itself, and the pathology information on the cellular nature of the tumor, we now have a far better means to plan a tailored, targeted treatment.
More importantly, Focal Laser Ablation is done under real-time MRI guidance, whereas cryo is guided by gray-scale ultrasound that only shows the leading edge of the iceball. While ultrasound-guided cryo may be adequate for whole-gland cryo, where precision is less of an issue, it has insufficient definition for a true focal treatment.
Focal Laser Ablation, on the other hand, can be image-monitored and tracked as it’s occurring, assuring that the laser has fully covered the desired zone of ablation. This allows us to avoid key urinary and sexual structures. Finally, we do not use general anesthesia.
Although Focal Laser Ablation does not yet have long term followup, our own early results are extremely promising. We expect as good, if not better, cancer control as any other ablation technology that uses thermal energy (extreme heat or cold). In fact, because of the high definition image monitoring as the treatment occurs, we have a high degree of confidence that we have destroyed the targeted cancer.
We are proud to have the most extensive experience with Focal Laser Ablation, a truly customized treatment that is a giant step forward in cancer treatment and men’s health.
[i] Ward J and Jones JS. Focal cryotherapy for localized prostate cancer: a report from the national Cryo On-Line Database (COLD) Registry. BJU Int. 2011;109:1648-54.