Phase III study results suggest that a hydrogel spacer developed to separate the rectum and prostate during radiotherapy for prostate cancer works to maintain bowel and urinary quality of life and reduces late rectal toxicity by 78% at 3 years post radiotherapy.
Phase III study results suggest the SpaceOAR System, a hydrogel spacer developed to separate the rectum and prostate during radiotherapy for prostate cancer, works to maintain bowel and urinary quality of life and reduces late rectal toxicity by 78% at 3 years post radiotherapy.
Providers, including urologists, inject the spacer as a liquid into the space between the prostate and rectum, where it creates a temporary space to reduce radiation to the anterior rectum. Leading U.S. cancer centers are already using the FDA-cleared technology, which solidifies into a soft hydrogel, remaining stable for 3 months. Then, it liquefies and is absorbed into the body.
The study, published in the International Journal of Radiation Oncology * Biology * Physics (2017; 97:976-85), looks at long-term results from a study of 222 men randomized two-to-one to receive the spacer or to the control group. Men in the study were treated with 79.2 Gy in 1.8-Gy fractions to the prostate, with or without the seminal vesicles.
The spacer reduced rectal V70 radiation dose by 73.5%, which resulted in reduced rectal toxicity. At a median 3 years post treatment, men receiving the SpaceOAR were 78% less likely to develop late rectal toxicity complications versus controls. None of the men in the SpaceOAR group had grade two or worse rectal toxicity, compared to 5.7% in the control group. In addition, mild urinary incontinence was 75% less likely in the spacer group, compared to controls. And, by 3 years, the average spacer patient bowel and urinary quality of life measure was like it was prior to radiotherapy, compared to control patients, whose long-term quality-of-life measures had significantly declined.
While one in five of the control patients had clinically significant quality-of-life declines in bowel, urinary, and sexual measures, only one in 40, or 2.5%, of men in the spacer group experienced those quality-of-life declines across all three domains.
The study’s lead author Daniel Hamstra, MD, PhD, of Beaumont Hospital, Dearborn, MI, told Urology Times that, for the clinical trial, men were eligible for treatment if they had low or intermediate-risk prostate cancer and were going to be treated with external beam radiotherapy, which in this case was intensity-modulated radiation therapy.
“They were excluded for large prostates of greater than 80 cc or for clear extra prostatic extension, T3,” he said.
Placing the spacer, he said, is typically done through a transperineal approach, using trans-rectal ultrasound guidance.
“This is similar to many other transperineal prostate procedures, such as template biopsies or brachytherapy. It is not particularly difficult to do for someone familiar with these types of procedures, but some training is required,” Dr. Hamstra said.
Next: "It is likely that the rates of very bad complications are small"
The potential downsides of using the spacer for prostate cancer patients include side effects and cost, although the authors did not see any severe side effects during the study, according to Dr. Hamstra.
“As a result, it is likely that the rates of very bad complications are small,” he said. “However, the use of the gel did decrease the chance of a serious toxicity in bowel function, as well as improved bowel and urinary patient-reported quality of life. Approximately four men (3.7) would have to be treated to prevent one man from having a measurable decline in bowel quality of life at 3 years, using a minimum threshold for change in bowel quality of life. And about six (6.3) would have to be treated with the gel to prevent a more serious decline in bowel quality of life at 3 years. I think these are not unreasonable numbers to treat with this treatment. Similar results were found for urinary quality of life.”
And while there is a cost for using the technology, the spacer is usually placed at the same time as when fiducial markers are placed in the prostate. So, adding the spacer does not result in the patient having to endure an extra procedure.
“The cost is not small, but relative to the total cost of radiotherapy for prostate cancer and relative to the cost of treating long-term side effects, I think the cost is really quite reasonable,” Dr. Hamstra said.
Dr. Hamstra was a paid consultant for Augmenix. Two of his co-authors have made small investments in Augmenix, one co-author has received a speaking honorarium and equity from Augmenix, and another co-author has provided consulting services for Augmenix.
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