Taussky Daniel, Haider Masoom, McLean Michael, Yeung Ivan, Williams Theresa, Pearson Shannon, Lockwood Gina, Crook Juanita
Department of Radiation Oncology, Princess Margaret Hospital, 610 University Avenue, Toronto, Ontario M5G 2M9, Canada.
Brachytherapy. 2004;3(3):125-9. doi: 10.1016/j.brachy.2004.06.004.
Erectile dysfunction following permanent seed brachytherapy for prostate cancer may be related to the dose to the penile bulb. We investigated anatomic and dosimetric factors that might contribute to an increased dose to the penile bulb.
One-month CT and MR images were examined for 50 consecutive patients treated with exclusive (125)I permanent seed prostate brachytherapy to a prescribed dose of 145 Gy. Implants were preplanned by transrectal ultrasound (TRUS). Postimplant dosimetry was performed at 1 month using an MRI-CT fusion. Spearman's correlation was used to establish a correlation between dosimetric parameters, anatomical factors, and the dose to the penile bulb.
Penile bulb volumes ranged from 1.2-8.5 cc (median, 3.9 cc). The distance from the penile bulb to the prostate apex ranged from 5-33 mm (median, 15.5 mm). D50 of the penile bulb ranged from 13-121 Gy. The range for the V45 (65 Gy) was 0-87%; only 3% of patients had >2 cc covered by this isodose and in 16% of patients the V45 covered more than 50% of the penile bulb. About one-third of the patients received a dose to the bulb that would put them at a high risk of erectile dysfunction after external beam radiation, if the dose were radiobiologically equivalent. There was a significant inverse correlation between the distance between the prostate apex and the penile bulb, and the dosimetric parameters of the bulb: r = -0.548, -0.656, p = < 0.01. The further caudal the apex was from the symphysis, the closer it was to the penile bulb (r = -0.564, p = <0.01). We could not find a correlation between the dose to the prostate or its apex and the dose to the penile bulb.
When the prostate apex is close to the penile bulb, care should be taken to limit the dose to the penile bulb, if possible. This may reduce the incidence of erectile dysfunction and urinary toxicity after permanent seed prostate brachytherapy.
前列腺癌永久性粒子近距离放射治疗后出现的勃起功能障碍可能与阴茎球部的剂量有关。我们研究了可能导致阴茎球部剂量增加的解剖学和剂量学因素。
对连续50例接受单纯¹²⁵I永久性粒子前列腺近距离放射治疗、处方剂量为145 Gy的患者进行了1个月后的CT和MR图像检查。植入治疗通过经直肠超声（TRUS）进行预计划。植入后1个月使用MRI-CT融合技术进行剂量测定。采用Spearman相关性分析来确定剂量学参数、解剖学因素与阴茎球部剂量之间的相关性。
阴茎球部体积范围为1.2 - 8.5立方厘米（中位数为3.9立方厘米）。阴茎球部到前列腺尖部的距离范围为5 - 33毫米（中位数为15.5毫米）。阴茎球部的D50范围为13 - 121 Gy。V45（65 Gy）的范围为0 - 87%；只有3%的患者该等剂量线覆盖体积大于2立方厘米，16%的患者V45覆盖了超过50%的阴茎球部。如果剂量在放射生物学上等效，约三分之一的患者接受的球部剂量会使他们在外照射放疗后有发生勃起功能障碍的高风险。前列腺尖部与阴茎球部之间的距离与球部的剂量学参数之间存在显著负相关：r = -0.548，-0.656，p = < 0.01。前列腺尖部离耻骨联合越靠尾侧，其离阴茎球部越近（r = -0.564，p = <0.01）。我们未发现前列腺或其尖部的剂量与阴茎球部的剂量之间存在相关性。
当前列腺尖部靠近阴茎球部时，应尽可能注意限制阴茎球部的剂量。这可能会降低永久性粒子前列腺近距离放射治疗后勃起功能障碍和泌尿毒性的发生率。
