MedicalResearch.com Interview with:
Daniel A. Hamstra, MD PhD
MedicalResearch.com: What is the background for the The SpaceOAR phase 3 trial study and the hydrogel spacer?
Response: External beam radiation therapy is commonly used to treat men with prostate cancer. As part of this treatment, side effects can occur involving bowel, urinary, and sexual symptoms.
This study was performed to test if an absorbable hydrogel placed between the prostate and rectum (using a simple outpatient procedure) could move the rectum away from the prostate and thus result in sparing of the rectum and decreased bowel toxicity. The study randomized 222 men and the three-year data were just published (The International Journal of Radiation Oncology Biology and Physics). With three years of follow-up, we saw that the spacer did improve the radiation plans and decreased both rectal toxicity and urinary toxicity.
MedicalResearch.com: What types of patients may benefit from use of the spacer during radiation therapy? What are the main findings of the study?
Response: In the previous analysis, we noted that the amount of radiation delivered to the base of the penis (penile bulb) was reduced with the use of the spacer. However, sexual function was not different between treatment arms. In the past, it has been shown that radiation to the area of the penile bulb is associated with decreased sexual function. We also noted that in the whole trial of 222 men more than half of the men had poor to very poor sexual function at the start of the study. So, in those men there was no chance to see a difference. Therefore, for the current analysis we limited the study to the 41% of men who had moderate to good sexual function as reported using a standardized quality of life questionnaire known as the EPIC.
When limited to men with better sexual function, we noted a number of things:
1) There was a correlation between dose to the penile bulb and sexual function. Higher dose was worse (this fits in with previous studies).
2) Men on the SpaceOAR arm had lower radiation dose to the penile bulb.
3) Men on the SpaceOAR arm had a very strong trend to better sexual function by average EPIC score over the three years of follow-up. They had a decline, but at three years this decline was about 13 points less than the control arm. This is an amount that would likely be important to most men. The difference was of borderline significance (p=0.07); perhaps because we only had 41% of the men who could be analyzed.
4) We also looked at the proportion of men with a meaningful change in EPIC score (defined as a decline of 11 or more points). In men with good sexual function at baseline this occurred in 75% of control men but 53% of Spacer men. Again, the p-value was borderline at 0.06.
Therefore, this is also suggestive that using the spacer may decrease the proportion of men with a significant decline in sexual function in the first three years.
5) Finally, we looked at the single question that asked men to define the character of their erections over the last four weeks. There were four answers: none, not enough for sexual activity, only enough for masturbation, or firm enough for intercourse. In men who had erections “firm enough for intercourse” to begin with, those treated with SpaceOAR maintained this ability 68% of the time at three years, while this was only true 38% of the time for the Control arm. This was statistically significant (p=0.03).
Our current analysis suggests that most men will likely benefit from the spacer by significantly decreasing their risk of bowel and urinary changes after RT. The new results from this study are that there is a suggestion that if men have good sexual function they may also see a benefit from the use of the Spacer. That was a new finding.
MedicalResearch.com: What recommendations do you have for future research as a result of this study?
Response: We were a bit surprised to find reduced penile bulb dose. This may occur because the spacer gel pushes the prostate away from the penile bulb a bit, or it may be that the radiation planning software was able to avoid the penile bulb a bit easier. Once we saw that difference, it seemed logical that there should be a difference in sexual function. The reason we had not seen it before was so many of the men had poor sexual function.
MedicalResearch.com: Is there anything else you would like to add?
Response: We would like to explore more the reason the penile bulb radiation dose was decreased by looking at the distance between this structure and the prostate based upon CT scans taken before and after the placement of the gel.
Disclosures: I serve as a paid consultant to Augmenix (who makes the SpaceOAR product). However, I had access to all study data and complete freedom to perform these analyses and to prepare the study. I have also served as a consultant for GenomeDX, Myriad, Medivation, and Bayer Health.
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Citation: ASCO 2017 Genitourinary Cancers Symposium 2017 abstract
J Clin Oncol 35, 2017 (suppl 6S; abstract 69)
Daniel A. Hamstra, Dhiren Shah, Steven Kurtzman, John Sylvester, Shawn H. Zimberg, Richard S. Hudes, Lawrence Ivan Karsh, Mark D. Logsdon, David Beyer, Michael Kos, R. Alex Hsi, Kevin Forsythe, Edward M Soffen, Patrick M Francke, Hong Zhang, Theodore L. DeWeese, Rodney J. Ellis, Jeffrey Bogart, Constantine Mantz, Neil Mariados; The Texas Center for Proton Therapy, Irving, TX; Western New York Urology Associates, Cheektowaga, NY; Urological Surgeons of Northern California, Inc., Campbell, CA; 21st Century Oncology, East Bradenton, FL; Advanced Radiation Centers of New York, Lake Success, NY; St. Agnes Hospital, Baltimore, MD; The Urology Center of Colorado, Denver, CO; Sutter Medical Group, Sacramento, CA; Arizona Oncology, Scottsdale, AZ; Urology Nevada, Reno, NV; Peninsula Cancer Center, Poulsbo, WA; Oregon Urology Institute, Springfield, OR; Princeton Radiation Oncology, Princeton, NJ; 21st Century Oncology, Coral Springs, FL; University of Rochester, Rochester, NY; The Sidney Kimmel Comprehensive Cancer Center at Johns Hopkins, Baltimore, MD; University Hospitals Case Medical Center, Case Comprehensive Cancer Center, Case Western Reserve University, Cleveland, OH; SUNY Upstate Medical University, Syracuse, NY; 21st Century Oncology, Fort Myers, FL; Associated Medical Professionals of New York, PLLC, Syracuse, NY
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