Balloon Device for Prostate Cancer Protects Rectum From Radiation

Becky McCall

March 29, 2011

March 29, 2011 (Vienna, Austria) — Insertion of ProSpace (Bioprotect), a biodegradable, inflatable balloon system, between prostate and rectum has been shown to reduce the volume of rectum exposed to D90 (approximately 70 Gy) radiation by 69.9%, according to results of a multicenter clinical trial presented here at the European Association of Urology (EAU) 26th Annual Congress by Fabrizio Dal Moro, MD, from the Department of Urology, Padova University Hospital, Italy.

"The results demonstrated that this balloon creates a distance between the prostate and the anterior wall of the rectum of a median of 1.9 cm. The effect is a dramatic reduction of radiation at the level of the anterior wall of the rectum, with a reduction of 69.9% in comparison to the same patient treated without this device," reported Dr. Dal Moro.

This study followed on from a feasibility study conducted in Israel in 7 patients. The 24 patients in the current study were recruited between 2009 and 2010 in Italy, Germany, the United States, and Israel.

The device is transperineally inserted between the prostate and the rectum wall before prostate radiotherapy to create a protective space and cause rectal separation. Using this method, the rectum is less exposed to radiation from external beam radiation treatment used for prostate cancer, Dr. Dal Moro explained.

With the patient in the lithotomy position, the device is inserted with the aid of transrectal ultrasound, using either a local anesthetic or general anesthesia, depending on patient choice.

Computed tomography or magnetic resonance imaging scans are performed before insertion of the balloon, and then again afterward. Five to 10 cc saline are injected under transrectal ultrasound guidance to help hydrodissect and delineate the area between the rectal fascia and the prostate, and the needle is then moved to the base of the prostate, near the seminal vesicles. An introducer is then inserted, followed by the balloon. To further track balloon stability, weekly computed tomography or ultrasound scans are carried out during radiotherapy, and then again at 3 and 6 months after implantation of the balloon.

Once positioned, the balloon dimensions were a median of 19.2 mm anterior-posteriorly, 30.5 mm wide, and 45 mm cranio-caudally, which created a significant separation between rectum and prostate. The separation resulted in a 69.9% reduction in rectum receiving 90% of the dose delivered to the prostate.

Study endpoints were balloon or procedure-related adverse events for safety, plus efficacy, which was defined as the percentage reduction in radiation exposure to the rectum at V50Gy, V60Gy, D100, D90, D70, and D50.

Dr. Dal Moro explained how the last 5 of the 24 cases only required local anesthesia, rather than general anesthesia. "There were 2 modalities for the insertion of the device. In the first modality, it can be inserted under general anesthesia with a dedicated template, but in our second modality, we insert under local anesthesia, using a 'free hand' approach. We insert the balloon in 15 minutes. There is no bleeding or intraperineal problems," he said.

Three patients who underwent general anesthesia developed urinary retention, which is a common adverse effect, and required catheterization. Pain levels were mild and lasted for a few hours, and no acute proctitis above grade 1 was observed for up to 3 months after radiotherapy in all patients, and up to the median follow-up of 6 months. Dr. Dal Moro added that this was significantly lower than the proctitis level recorded in literature on similar procedures.

Weekly computed tomography or ultrasound scans revealed that the balloon had maintained stable separation and had not altered shape in all 24 patients. Premature deflation only occurred in 3 cases, after the introduction of fiducial markers transrectally. This did not occur when the markers were inserted transperineally. "There are several attempts by different gel-like substances to create this separation, but the gel cannot maintain its shape during radiation like the balloon," said Dr. Dal Moro.

"So we can conclude that it is a very good device when considering safety. It is easy to perform, easy to implant, and easy to learn. It is not associated with discomfort for the patient, and in terms of efficacy, the numbers demonstrate a very dramatic reduction of dosage. And as it is now commercially available in the European community for routine use, it could be used for testing higher doses for more aggressive radiation with fewer side effects with newer radiation technologies in the near future," remarked Dr. Dal Moro.

Addressing the speaker and those gathered at the session, Sophie Fossa, MD, oncologist from the Norwegian Radium Hospital, Oslo, raised the issue of patient discomfort related to the balloon during the time in situ. "This treatment with the balloon can take about 2.5 months, so the patient has the balloon [in place] for this length of time at least. I would like to know if patients have experienced any problems with bowel functions. I think they might, and I'd like to know how this was tolerated," she commented.

Dr. Dal Moro replied that the balloon was inflated with 16 mL saline, and that this volume did not precipitate any kind of problem with bowel function. "Patients have not reported any discomfort. In 3 to 6 months, the balloon is deflated, and then ultrasound shows it disappears after this period of time."

Anthony Zietman, MD, Shipley Professor of Radiation Oncology from Harvard Medical School, Boston, Massachusetts, noted that this device, among other similar ones, might address a key issue with treating a prostate that frequently changes position. "One major problem that arises when treating a prostate with radiotherapy is that the prostate moves from day to day, according to filling of the bladder and rectum, and limits the accuracy of the treatment. It is tough to treat a moving target. This study reports one of several simple and ingenious methods now available to both stabilize the position of the prostate and separate it from the rectum, keeping the latter out of the line of fire," he commented.

Dr. Dal Moro, Dr. Fossa, and Dr. Zietman have disclosed no relevant financial relationships.

European Association of Urology (EAU) 26th Annual Congress. Presented March 21, 2011.

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