Kole Thomas P, Tong Michael, Wu Binbin, Lei Siyuan, Obayomi-Davies Olusola, Chen Leonard N, Suy Simeng, Dritschilo Anatoly, Yorke Ellen, Collins Sean P
a Department of Radiation Medicine , Georgetown University Hospital , Washington , DC , USA.
b Department of Radiation Oncology , Memorial Sloan-Kettering Cancer Center , New York, New York , USA.
Acta Oncol. 2016;55(1):52-8. doi: 10.3109/0284186X.2015.1037011. Epub 2015 May 14.
Late urinary symptom flare has been shown to occur in a small subset of men treated with ultra- hypofractionated stereotactic body radiotherapy (SBRT) for prostate cancer. The purpose of this study was to use normal tissue complication probability modeling in an effort to derive SBRT specific dosimetric predictor's of late urinary flare.
Two hundred and sixteen men were treated for localized prostate cancer using ultra- hypofractionated SBRT. A dose of 35-36.25 Gy in 5 fractions was delivered to the prostate and proximal seminal vesicles. Functional surveys were conducted before and after treatment to assess late toxicity. Phenomenologic NTCP models were fit to bladder DVHs and late urinary flare outcomes using maximum likelihood estimation.
Twenty-nine patients experienced late urinary flare within two years of completion of treatment. Fitting of bladder DVH data to a Lyman NTCP model resulted in parameter estimates of m, TD50, and n of 0.19 (0-0.47), 38.7 Gy (31.1-46.4), and 0.13 (-0.14-0.41), respectively. Subsequent fit to a hottest volume probit model revealed a significant association of late urinary flare with dose to the hottest 12.7% of bladder volume. Multivariate analysis resulted in a final model that included patient age and hottest volume probit model predictions. Kaplan-Meier analysis demonstrated a two-year urinary flare free survival of 95.7% in patients 65 years or older with a bladder D12.7% of 33.5 Gy or less, compared to 74.5% in patients meeting none of these criteria.
NTCP modeling of late urinary flare after ultra-hypofractionated prostate SBRT demonstrates a relatively small volume effect for dose to the bladder, suggesting that reduction of volume receiving elevated dose will result in decreased incidence of late urinary toxicity. Future studies will be needed to examine the impact of dose to other potential sources of late genitourinary toxicity.
晚期尿路症状复发已被证实发生在一小部分接受超分割立体定向体部放疗（SBRT）治疗前列腺癌的男性患者中。本研究的目的是使用正常组织并发症概率模型，以得出SBRT特有的晚期尿路复发剂量学预测指标。
216名男性患者接受了超分割SBRT治疗局限性前列腺癌。给予前列腺和近端精囊5次分割共35 - 36.25 Gy的剂量。在治疗前后进行功能调查以评估晚期毒性。使用最大似然估计法将现象学NTCP模型拟合到膀胱剂量体积直方图（DVH）和晚期尿路复发结果。
29名患者在完成治疗后的两年内出现晚期尿路复发。将膀胱DVH数据拟合到Lyman NTCP模型，得到的参数估计值为：m为0.19（0 - 0.47），TD50为38.7 Gy（31.1 - 46.4），n为0.13（ - 0.14 - 0.41）。随后拟合到最热体积概率模型显示，晚期尿路复发与膀胱最热12.7%体积的剂量有显著关联。多变量分析得出最终模型，该模型包括患者年龄和最热体积概率模型预测值。Kaplan - Meier分析表明，膀胱D12.7%为33.5 Gy或更低的65岁及以上患者，两年无尿路复发生存率为95.7%，而不符合这些标准的患者为74.5%。
超分割前列腺SBRT后晚期尿路复发的NTCP模型显示，膀胱剂量的体积效应相对较小，这表明减少接受高剂量的体积将导致晚期尿路毒性发生率降低。未来需要进一步研究来探讨其他潜在的晚期泌尿生殖系统毒性来源的剂量影响。
