The aim of the present study was to report on our early experience with hydrogel spacer (SpaceOAR) placement in combination with iodine-125 low-dose-rate brachytherapy for prostate cancer.

From April 2018, SpaceOAR hydrogel spacer was placed in 100 consecutive patients undergoing iodine-125 low-dose-rate brachytherapy. Complications and the status of the placement were evaluated. Deformation of the prostate by the spacer was examined measuring prostate diameters and evaluating the change from preoperative status. The position of the prostate was similarly examined by evaluating the change in distance between the pubic symphysis and the prostate. Post-plan dosimetric data were compared with 200 patients treated without a spacer.

No complications were found during either the intraoperative or perioperative periods. The mean displacement distance of 11.64 mm was created, the mean value before spacer placement was 0.28 mm (P < 0.0001). The change of the prostate diameters showed a positive increase in all directions, with no significant negative change in any one direction. Regarding the change in distance between pubic symphysis and the prostate, no significant shortening trend was observed between the two groups (P = 0.14). Whereas the dosimetric parameters showed means of 0.001 and 0.026 cc for RV150 and RV100 in the spacer group, they were 0.025 and 0.318 cc, respectively, in the non-spacer group, showing a significant decrease in both parameters (P < 0.001).

Prostate deformation secondary to hydrogel placement might adversely affect dosimetric parameters in patients undergoing low-dose-rate brachytherapy. However, a significant reduction in the rectal dose can be adopted without adversely affecting the other parameters related to treatment outcome.

International journal of urology : official journal of the Japanese Urological Association. 2019 Oct 06 [Epub ahead of print]

Masashi Morita, Takashi Fukagai, Kidai Hirayama, Jin Yamatoya, Tetsuo Noguchi, Yu Ogawa, Atsushi Igarashi, Akifumi Niiya, Masako Kato, Madoka Morota, Kazuhiko Oshinomi, Yoshio Ogawa, John L Lederer

Department of Urology, Showa University Koto Toyosu Hospital, Tokyo, Japan., Department of Radiation Oncology, Showa University Koto Toyosu Hospital, Tokyo, Japan., Division of Radiation Oncology, Department of Radiology, Showa University School of Medicine, Tokyo, Japan., Department of Urology, Showa University School of Medicine, Tokyo, Japan., Department of Surgery, John A. Burns School of Medicine, University of Hawai’i at Manoa, Honolulu, Hawaii, USA.