Xiang Hong F, Lu Hsiao-Ming, Efstathiou Jason A, Zietman Anthony L, De Armas Ricardo, Harris Kathryn, Bloch B Nicolas, Qureshi Muhammad Mustafa, Keohan Sean, Hirsch Ariel E
Department of Radiation Oncology, Boston University School of Medicine and Boston Medical Center, Boston, Massachusetts, USA.
Department of Radiation Oncology, Massachusetts General Hospital and Harvard Medical School, Boston, Massachusetts, USA.
J Appl Clin Med Phys. 2017 May;18(3):37-43. doi: 10.1002/acm2.12063. Epub 2017 Apr 13.
In SBRT for prostate cancer, higher fractional dose to the rectum is a major toxicity concern due to using smaller PTV margin and hypofractionation. We investigate the dosimetric impact on rectum using endorectal balloon (ERB) in prostate SBRT.
Twenty prostate cancer patients were included in a retrospective study, ten with ERB and 10 without ERB. Optimized SBRT plans were generated on CyberKnife MultiPlan for 5 × 7.25 Gy to PTV under RTOG-0938 protocol for early-stage prostate cancer. For the rectum and the anterior half rectum, mean dose and percentage of volumes receiving 50%, 80%, 90%, and 100% prescription dose were compared.
Using ERB, mean dose to the rectum was 62 cGy (P = 0.001) lower per fraction, and 50 cGy (P = 0.024) lower per fraction for the anterior half rectum. The average V , V , V , and V were lower by 9.9% (P = 0.001), 5.3% (P = 0.0002), 3.4% (P = 0.0002), and 1.2% (P = 0.005) for the rectum, and lower by 10.4% (P = 0.009), 8.3% (P = 0.0004), 5.4% (P = 0.0003), and 2.1% (P = 0.003) for the anterior half rectum.
Significant reductions of dose to the rectum using ERB were observed. This may lead to improvement of the rectal toxicity profiles in prostate SBRT.
在前列腺癌的立体定向体部放疗（SBRT）中，由于计划靶体积（PTV）边界较小及大分割放疗，直肠接受的较高分次剂量是一个主要的毒性问题。我们研究了在前列腺SBRT中使用直肠内气囊（ERB）对直肠剂量学的影响。
一项回顾性研究纳入了20例前列腺癌患者，其中10例使用ERB，10例未使用ERB。根据RTOG-0938方案，在射波刀多叶准直器（CyberKnife MultiPlan）上为早期前列腺癌的PTV生成优化的SBRT计划，处方剂量为5×7.25 Gy。比较直肠和直肠前半部分的平均剂量以及接受50%、80%、90%和100%处方剂量的体积百分比。
使用ERB时，直肠的平均分次剂量降低62 cGy（P = 0.001），直肠前半部分的平均分次剂量降低50 cGy（P = 0.024）。直肠的平均V50、V80、V90和V100分别降低9.9%（P = 0.001）、5.3%（P = 0.0002）、3.4%（P = 0.0002）和1.2%（P = 0.005），直肠前半部分分别降低10.4%（P = 0.009）、8.3%（P = 0.0004）、5.4%（P = 0.0003）和2.1%（P = 0.003）。
观察到使用ERB可显著降低直肠剂量。这可能会改善前列腺SBRT中直肠的毒性情况。
