Patil Nikhilesh, Crook Juanita, Saibishkumar Elantholi P, Aneja Manipdip, Borg Jette, Pond Greg, Ma Clement
Department of Radiation Oncology, Princess Margaret Hospital, University Health Network, Toronto, Canada.
Department of Radiation Oncology, Princess Margaret Hospital, University Health Network, Toronto, Canada.
Brachytherapy. 2009 Apr-Jun;8(2):218-222. doi: 10.1016/j.brachy.2008.12.001. Epub 2009 Feb 20.
Men with higher body mass index (BMI) tend to have more fatty tissue in prostate-rectum interface, which may reduce the rectal wall dose by the inverse square law. We hypothesized that men with higher BMI will have a lower dose to the rectal wall and less rectal toxicity after permanent prostate implant.
Prospectively collected data on rectal dosimetry/toxicity and BMI of 407 patients who underwent iodine-125 ((125)I) prostate implant were analyzed. Postimplant dosimetry used CT-MRI fusion on Day 30. Rectal wall was contoured on all slices where seeds were seen. The volume of rectal wall receiving the prescribed dose (RV(100) in cm(3)) and the dose to 1cc of rectal wall (RD(1cc)) were reported. Other factors evaluated for association with rectal dosimetry and toxicity included age, diabetes, hypertension, smoking, use of neoadjuvant hormones, T stage, baseline prostate volume, 1 month prostate edema, seed type and activity, and prostate dosimetry factors (the isodose enclosing 90% of the prostate volume [D(90)], the percentage of the prostate volume enclosed by the prescription [V(100)], and the percentage of the prostate volume enclosed by the 150% isodose [V(150)]). Rectal toxicity was reported as per Radiation Therapy Oncology Group criteria.
BMIs ranged from 15.9 to 46.8 (mean+/-standard deviation [SD]: 27.8+/-4.2). The mean+/-SD values for RV(100) and RD(1cc) were 0.79+/-0.49cm(3) and 128.2+/-27.8Gy, respectively. There was a significant negative association of BMI with RV(100) (p=0.007) and RD(1cc) (p=0.01) on univariate analysis. The mean RV(100) and RD(1cc) for men with higher BMI (>27.8) were lower compared with their slimmer counterparts (0.70 vs. 0.86cm(3) and 123.4 vs. 132.4Gy, respectively). On multivariate analysis for RV(100) and RD(1cc), BMI remained significant (p-values 0.004 and 0.01, respectively) along with prostate volume and V(150), suggesting that anatomic factors are important in rectal dosimetry in prostate brachytherapy. Overall the incidence of Radiation Therapy Oncology Group acute rectal toxicity was 12% (Grade 2, 1.3%) and chronic 6% (Grade 2, 0.5%). No Grade 3 toxicity occurred. None of the factors evaluated were predictive for rectal toxicity.
Men with a lower BMI received a higher rectal wall dose compared with those with higher BMI. This did not, however, translate into greater rectal toxicity.
体重指数（BMI）较高的男性前列腺 - 直肠界面往往有更多脂肪组织，这可能根据平方反比定律降低直肠壁剂量。我们假设BMI较高的男性永久性前列腺植入术后直肠壁剂量较低且直肠毒性较小。
对前瞻性收集的407例行碘 - 125（¹²⁵I）前列腺植入患者的直肠剂量测定/毒性和BMI数据进行分析。植入后30天使用CT - MRI融合进行剂量测定。在可见籽源的所有层面勾勒直肠壁轮廓。报告接受处方剂量的直肠壁体积（RV(100)，单位为cm³）和1cc直肠壁的剂量（RD(1cc)）。评估与直肠剂量测定和毒性相关的其他因素包括年龄、糖尿病、高血压、吸烟、新辅助激素的使用、T分期、基线前列腺体积、1个月时前列腺水肿、籽源类型和活度以及前列腺剂量测定因素（包围90%前列腺体积的等剂量线[D(90)]、处方剂量包围的前列腺体积百分比[V(100)]以及150%等剂量线包围的前列腺体积百分比[V(150)]）。根据放射治疗肿瘤学组标准报告直肠毒性。
BMI范围为15.9至46.8（均值±标准差[SD]：27.8±4.2）。RV(100)和RD(1cc)的均值±SD值分别为0.79±0.49cm³和128.2±27.8Gy。单因素分析显示BMI与RV(100)（p = 0.007）和RD(1cc)（p = 0.01）存在显著负相关。BMI较高（>27.8）的男性的平均RV(100)和RD(1cc)低于体型较瘦的男性（分别为0.70 vs. 0.86cm³和123.4 vs. 132.4Gy）。对RV(100)和RD(1cc)进行多因素分析时，BMI以及前列腺体积和V(150)仍然具有显著性（p值分别为0.004和0.01），表明解剖学因素在前列腺近距离治疗的直肠剂量测定中很重要。总体而言，放射治疗肿瘤学组急性直肠毒性的发生率为12%（2级，1.3%），慢性毒性为6%（2级，0.5%）。未发生3级毒性。所评估的因素均不能预测直肠毒性。
与BMI较高的男性相比，BMI较低的男性接受的直肠壁剂量更高。然而，这并未转化为更大的直肠毒性。
