The patient characteristics are shown in Table. The median age at baseline, median prostate-specific-antigen (PSA) at diagnosis of prostate cancer, and median prostate volume at LDR-BT were 66 years (interquartile range [IQR]; 62-71 years), 6.4 ng/mL (IQR; 5.1-9.0 ng/ mL) and 22.5 mL (range; 17.7-29.1 mL), respectively in non-SpaceOAR group and 72 years (IQR; 61.3-71 years), 7.3 ng/ mL (IQR; 5.8-10.6 ng/ mL) and 27.3 mL (range; 21.4-31.8 mL), respectively in SpaceOAR group. The LDR-BT + EBRT consisted of 192 patients (42.4%) in non-SpaceOAR group and 16 patients (53.3%) in SpaceOAR group. The median IPSS, OABSS, IPSS-QOL, maximum flow rate (Qmax), voided volume (VV), and PVR before LDR-BT were 5 (IQR; 3-9), 3 (IQR; 2-4), 2 (IQR; 1-3), 17.6 mL/s (IQR; 14.5-21.7 mL/s), 250 mL (IQR; 183-349 mL) and 15.0 mL (IQR; 3.9-30 mL), respectively in non-SpaceOAR group and 7 (IQR; 3-10), 3 (IQR; 2-5), 3 (IQR; 1-4), 15.1 mL/s (IQR; 11.7-19.1 mL/s), 177.8 mL (IQR; 125.8-292.5 mL) and 30 mL (IQR; 2.0-52.5 mL), respectively in SpaceOAR group. There were no significant differences of D90, V100, and UD30 between two groups, while RV100 (p<0.001) and RV150 (p=0.033) were significantly lower in SpaceOAR group.
Both in non-SpaceOAR group and SpaceOAR group, IPSS, OABSS, and IPSS-QOL increased at 3 months after LDR-BT, and the scores decreased at 12 months. Analysis of variance revealed that follow-up time was significantly related change of IPSS, OABSS, and IPSS-QOL (p<0.001, p<0.001 and p<0.001, respectively). SpaceOAR did not show significant differences in relationship between follow-up time and following factors, IPSS, OABSS and IPSS-QOL. Although transient deterioration of Qmax and VV were observed, all factors recovered in 6 to 9 months after LDR-BT in both group. Analysis of variance revealed that follow-up time was significantly related changes of PVR (p<0.001). Interestingly, the use of SpaceOAR significantly affected chronological change in PVR (p=0.001). The least square mean of PVR in SpaceOAR group was significantly increased compared with non-SpaceOAR group at 3 months after LDR-BT (49.8mL vs 30.5mL, p=0.002).