Imaging Prostate Cancer
Posted: Nov 01, 2018
POSTED: September 14, 2018
Dr. Neil Desai, an Assistant Professor of radiation oncology at the University of Texas Southwestern Medical Center, specializes in treating genitourinary cancers.
Prostatepedia with him about his clinical trial looking at erectile dysfunction in men after nerve sparing stereotactic ablative body radiotherapy (SABR) for localized prostate cancer.
Dr. Desai: The focus on sexual dysfunction after treatment for prostate cancer is not a new one. We have gotten better about cure rates, risk classification schemes using genomics and other clinical factors, and about managing urinary and rectal side effects.
Sexual dysfunction after treatment, however, remains a common reality that we force men to accept with preparation that is never sufficient. It’s an especially mean kind of change when you’re talking about men who are at the point of their lives where they’re becoming able again to focus on themselves— maybe the kids are out of the house and they’re in their last five to 10 years of potency. Then you take that away from them.
This glaring deficiency in progress and a nihilism about ways to address it seemed to my collaborators and me to contrast against large strides in imaging, treatment precision of radiotherapy, and understanding of the key anatomy mediating sexual dysfunction after radiation.
In particular, there is apparent synergy from improved localization of clinically significant disease within the prostate gland by MRI, ability to deliver radiation with precision in the millimeter range, and introduction of a rectal spacer gel that allows freedom to focus on sparing other nearby anatomy like vessels and nerves involved in sexual function. Armed with these complementary advances, we aimed to try again to tackle the problem of sexual dysfunction.
Thus, we can’t really say this is a novel idea. We simply believe we are at an inflection point where technology has shifted just enough where we can look back at a good question from 10 years ago but with better technology and understanding to maybe make more of a difference.
Dr. Desai: Before entering the trial, we critically interrogate a man’s disease and sexual function to make sure we can safely and meaningfully offer them a potential benefit for enrolling. The main question is do they have a disease that’s amenable to a dose de-escalation design? Can we at least de-escalate the intensity of treatment on at least one side of the prostate in an effort to spare the nerve bundles there, as well as some critical vessels that may relate to sexual function—or is their disease too close to be safe? Did the rectal spacer gel insertion adequately displace the rectum to allow us the luxury to consider de-escalating a neurovascular bundle and other vessels opposite to a man’s dominant disease?
Once satisfied, these requirements are met, the man is randomized to either standard SABR, or an SABR technique that will de-escalate the dose to the side of the prostate opposite dominant disease and next to a neurovascular bundle. As there may yet be clinically indolent disease below the MRI threshold of detection in this region, we are still treating the prostate in this area to a minimum dose we feel can still address such lower grade disease.
The dose de-escalation technique will be used in half the patients, and they will not know which arm they are in (blinding), in order to preserve the integrity of the assessment of whether this technique actually reduces sexual dysfunction.
Men will then be followed per standard follow-up at regular intervals with PSA testing, exam and quality of life questionnaires assessing changes in sexual function and medication requirement.