Relationship between radiation doses and development of erectile dysfunction in patients treated with permanent prostate brachytherapy for localized prostate cancer
Hayakawa, N1; Kikuchi, E1; Shigeta, K1; Mizuno, R1; Oya, M1
1: Keio University School of Medicine, Japan
Objective: We evaluated the effect of radiation doses on the development of brachytherapy-induced erectile dysfunction by using the International Index of Erectile Function-15 (IIEF-15) in a longitudinal prospective study.
Material and Method: We identified 48 patients without any supplemental therapy who had a sufficient potency before undergoing prostate brachytherapy (defined as EF score ≥11). Prostate brachytherapy (PB) was administered via transperitoneal approach using 125-I radioactive free seeds with a prescription dose of from 145Gy to 160Gy. Dosimetric parameters were collected as follows; mean dose to 90% of prostate volume (total D90), percentage of prostate volume receiving at least 100% dose (total V100), and receiving at least 150% dose (total V150). We also defined prostate apex as a 10 mm range from the distal edge of the prostate, and constructed a 3D model of the prostate and rectum for evaluating the radiation dose and exposed area. We prospectively collected IIEF-15 questionnaires before and every 3 months after PB for at least 2 years after treatment. We defined an EF domain score change to less than 10 as worsened EF severity.
Results: Total IIEF-15 score was 49.9±12.0 before PB, but decreased to 34.7±20.3 12 months after PB (p<0.05). In 48 patients, 32 (75.0%) had a deterioration of their EF score 12 months after PB. Mean age in the worsened EF severity group was 63.9 years, which was significantly lower than that in their counterparts (67.8 years, p=0.029). Furthermore, 47.9% and 58.3% of patients in the worsened EF severity group had significantly more total V100 ≥95% and apex V150 ≥70%, respectively, as compared to those in their counterparts (12.5%, p=0.024 and 18.3%, p=0.003, respectively). Multivariate analysis identified ≥70 years old and apex V150 ≥70% as independent predictors of deteriorated EF severity 12 months after PB (p=0.024, HR=7.9, p=0.007, HR=7.8, respectively).
Conclusion: An excessive dose of radiation to the apex area of the prostate and advanced age might have an influence on worsening potency preservation after PB.
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