Prostate cancer tool may cut risk for women in radiation therapy
Long-lasting gel spacer guards healthy tissue during treatment
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A long-lasting gel used to help protect the bowel during radiation therapy for prostate cancer may be successfully used in women with gynecological cancers undergoing MRI-guided internal radiation treatment, or brachytherapy, according to a small study from Australia.
The study found that placing the gel, known as a rectal spacer, between the rectum and the radiation target was safe, easy to perform, and effective at increasing the distance between healthy tissue and the area to be treated.
The spacer, made of a stabilized form of hyaluronic acid — a substance naturally found in the body that helps retain moisture and cushion tissues — remained stable throughout treatment, avoiding the need for repeated injections required with some previously used hyaluronic acid–based spacers.
The researchers said the findings support the feasibility of using a stabilized hyaluronic acid gel spacer during MRI-guided brachytherapy for gynecological cancers, though they added that larger studies are needed “to determine the efficacy and patient suitability” of spacer use.
The study, “Stabilised Hyaluronic Acid Gel Rectal Spacers in MRI-Guided Brachytherapy for Gynaecological Cancers: A Prospective Feasibility Study,” was published in the Journal of Medical Radiation Sciences.
Protecting the bowel
MRI-guided brachytherapy is a common treatment for gynecological cancers such as cervical and vaginal cancer. It uses detailed MRI scans to guide sources of radiation therapy inside the body, close to the tumor, allowing for high radiation doses while limiting exposure to nearby healthy organs.
Even with this targeted approach, the rectum can be exposed to radiation, which may lead to bowel-related side effects. Reducing damage to healthy tissue while maintaining effective cancer control remains an important goal.
In prostate cancer, rectal spacers made of hyaluronic acid are widely used to protect the rectum during radiation therapy. While similar spacers have been used off-label in gynecological brachytherapy, they are absorbed quickly and often require repeated injections at each treatment session. This need increases the risk of infection and injury to nearby organs and limits their use over longer treatment courses.
The use of longer-lasting spacers made of stabilized hyaluronic acid (sHA) has not yet been studied in gynecological cancers.
To explore the feasibility of this approach, the researchers conducted a prospective study (ACTRN12625000167460) involving 12 women with gynecological cancers who underwent MRI-guided high-dose-rate brachytherapy at a single center in Australia. Participants were enrolled from May 2024 to February 2025.
Eleven women had cervical cancer, while one had vaginal cancer. The mean age at diagnosis was 44.5, with ages ranging from 35 to 59.
All women received standard external radiation therapy five days a week before brachytherapy, with chemotherapy given at the same time. Half then completed three brachytherapy treatment sessions, while the other half had four. The full course of treatment lasted a mean of 50 days, or about seven weeks.
In 10 of the 12 cases, the gel spacer was placed during the second brachytherapy session. The procedure was performed under general anesthesia, with doctors using real-time ultrasound imaging to guide the injection of the gel through a thin needle into the space between the vagina and rectum, or rectovaginal space.
Spacer placement was successful in all 12 patients, meeting the study’s main goal. The gel spacer was inserted through the vagina in 10 women and through the perineum (the area of skin between the vagina and the anus) in two. The procedure added a mean of 26 minutes to standard brachytherapy treatment.
MRI scans confirmed correct spacer placement in every case. No side effects were reported on the day of insertion, during subsequent brachytherapy sessions, or by the end of treatment.
All women felt moderately or very confident in carrying the spacer, with none reporting pain or heaviness related to it.
Doctors reported that assembly and use of the gel spacer were easy (75%) or very easy (25%). They rated ultrasound image quality during placement as good or excellent in 9 of 12 patients (75%) and reported that the gel spacer was visible or clearly visible in all cases. The procedure was straightforward to integrate into the standard brachytherapy workflow, the doctors said.
Placement of the spacer led to a clear and lasting increase in the distance between the rectum and the radiation target. Before spacer placement, the mean target-to-rectum distance was 15.45 mm. After spacer insertion, the distance increased to a mean of 23.27 mm at the first brachytherapy session and 24.09 mm at the final session, representing a mean increase of 7.82 mm.
MRI scans showed that the gel spacer gradually decreased in size over the course of treatment. Despite this reduction, there was no significant change in the target-to-rectum distance.
“This study supports the feasibility of inserting sHA into the rectovaginal space in [gynecological cancer high-dose-rate brachytherapy],” the researchers wrote.
