Yondorf Menachem Z, Faraz Shahdabul, Smith Andrew W, Sabbas Albert, Parashar Bhupesh, Schwartz Theodore H, Wernicke A Gabriella
Department of Radiation Oncology, Weill Medical College of Cornell University, New York, USA.
Department of Radiation Oncology, Thomas Jefferson University Hospital, Philadelphia, USA.
J Contemp Brachytherapy. 2020 Aug;12(4):311-316. doi: 10.5114/jcb.2020.98109. Epub 2020 Aug 21.
To compare treatment plans and evaluate dosimetric characteristics of permanent cesium-131 (Cs) vs. iodine-125 (I) implants used in brain brachytherapy.
Twenty-four patients with Cs implants from a prospective phase I/II trial were re-planned with I implants. In order to evaluate the volume of brain tissue exposed to radiation therapy (RT), the dose volume histogram was generated for both radioisotopes. To evaluate the dosimetric differences of the two radioisotopes we compared homogeneity (HI) and conformity indices (CI), and dose covering 100% (D), 90% (D), 80% (D), and 50% (D) of the clinical target volume (CTV).
At the 100%, 90%, 80%, and 50% isodose lines, the Cs plans exposed less mean volume of brain tissue than the I plans ( < 0.001). The D, D, D, and D were smaller for Cs ( < 0.001). The HI and CI for Cs vs. I were 19.71 vs. 29.04 and 1.31 vs. 1.92, respectively ( < 0.001).
Compared to I, Cs exposed smaller volumes of brain tissue to equivalent doses of radiation and delivered lower radiation doses to equivalent volumes of the CTV. Cs exhibited a higher HI, indicating increased uniformity of doses within the CTV. Lastly, Cs presented a CI closer to 1, indicating that the total volume receiving the prescription dose was closer to the desired CTV volume. These results suggest that Cs is dosimetrically superior to I and may explain the reason for the 0% incidence of radiation necrosis (RN) in our previously published prospective study using Cs.
比较脑部近距离放射治疗中使用的永久性铯 - 131（Cs）与碘 - 125（I）植入物的治疗计划，并评估其剂量学特征。
对一项前瞻性I/II期试验中接受Cs植入的24例患者重新制定I植入物的治疗计划。为了评估接受放射治疗（RT）的脑组织体积，针对两种放射性同位素生成剂量体积直方图。为了评估两种放射性同位素的剂量学差异，我们比较了均匀性指数（HI）和适形指数（CI），以及覆盖临床靶体积（CTV）100%（D）、90%（D）、80%（D）和50%（D）的剂量。
在100%、90%、80%和50%等剂量线处，Cs计划所暴露的脑组织平均体积比I计划小（<0.001）。Cs的D、D、D和D较小（<0.001）。Cs与I的HI和CI分别为19.71对29.04以及1.31对1.92（<0.001）。
与I相比，Cs使等量辐射剂量下的脑组织暴露体积更小，并且向等量CTV体积输送的辐射剂量更低。Cs表现出更高的HI，表明CTV内剂量均匀性增加。最后，Cs的CI更接近1，表明接受处方剂量的总体积更接近期望的CTV体积。这些结果表明，Cs在剂量学上优于I，这可能解释了我们先前发表的使用Cs的前瞻性研究中放射性坏死（RN）发生率为0%的原因。
