Annede Pierre, Dumas Isabelle, Schernberg Antoine, Tailleur Anne, Fumagalli Ingrid, Bockel Sophie, Mignot Fabien, Kissel Manon, Deutsch Eric, Haie-Meder Christine, Chargari Cyrus
Radiotherapy Department, Brachytherapy Unit, Gustave Roussy Cancer Campus, Villejuif, France.
Radiotherapy Department, Brachytherapy Unit, Gustave Roussy Cancer Campus, Villejuif, France; INSERM U1030, Gustave Roussy Cancer Campus, Villejuif, France.
Brachytherapy. 2019 May-Jun;18(3):370-377. doi: 10.1016/j.brachy.2018.12.009. Epub 2019 Feb 21.
Only scarce data are available on the possibility to include radiobiological optimization as part of the dosimetric process in cervical cancer treated with brachytherapy (BT). We compared dosimetric outcomes of pulse-dose-rate (PDR) and high-dose-rate (HDR)-BT, according to linear-quadratic model.
Three-dimensional dosimetric data of 10 consecutive patients with cervical cancer undergoing intracavitary image-guided adaptive PDR-BT after external beam radiation therapy were examined. A new HDR plan was generated for each patient using the same method as for the PDR plan. The procedure was intended to achieve the same D high-risk clinical target volume with HDR as with PDR planning after conversion into dose equivalent per 2 Gy fractions (EQD2) following linear-quadratic model. Plans were compared for dosimetric variables.
As per study's methodology, the D high-risk clinical target volume was strictly identical between PDR and HDR plans: 91.0 Gy (interquartile: 86.0-94.6 Gy). The median D intermediate-risk clinical target volume was 62.9 Gy with HDR vs. 65.0 Gy with PDR (p < 0.001). The median bladder D was 65.6 Gy with HDR, vs. 62 Gy with PDR (p = 0.004). Doses to the rectum, sigmoid, and small bowel were higher with HDR plans with a median D of 55.6 Gy (vs. 55.1 Gy, p = 0.027), 67.2 Gy (vs. S 64.7 Gy, p = 0.002), and 69.4 Gy (vs. 66.8 Gy, p = 0.014), respectively. For organs at risk (OARs), the effect of radiobiological weighting depended on the dose delivered. When OARs BT contribution to D doses was <20 Gy, both BT modalities were equivalent. OARs EQD2 doses were all higher with HDR when BT contribution to D was ≥20 Gy.
Both BT modalities provided satisfactory target volume coverage with a slightly higher value with the HDR technique for OARs D2 while intermediate-risk clinical target volume received higher dose in the PDR plan. The radiobiological benefit of PDR over HDR was predominant when BT contribution dose to OARs was >20 Gy.
关于在宫颈癌近距离放疗（BT）中纳入放射生物学优化作为剂量测定过程一部分的可能性，仅有稀缺数据。我们根据线性二次模型比较了脉冲剂量率（PDR）和高剂量率（HDR）-BT的剂量测定结果。
检查了10例连续宫颈癌患者在体外放射治疗后接受腔内图像引导自适应PDR-BT的三维剂量测定数据。使用与PDR计划相同的方法为每位患者生成一个新的HDR计划。该程序旨在按照线性二次模型转换为每2Gy分次的剂量当量（EQD2）后，使HDR与PDR计划达到相同的高危临床靶体积D。比较计划的剂量测定变量。
根据研究方法，PDR和HDR计划之间的高危临床靶体积D严格相同：91.0Gy（四分位间距：86.0 - 94.6Gy）。HDR的中危临床靶体积中位数为62.9Gy，而PDR为65.0Gy（p < 0.001）。膀胱D的中位数HDR为65.6Gy，PDR为62Gy（p = 0.004）。HDR计划对直肠、乙状结肠和小肠的剂量更高，中位数D分别为55.6Gy（vs. 55.1Gy，p = 0.027）、67.2Gy（vs. S64.7Gy，p = 0.002）和69.4Gy（vs. 66.8Gy，p = 0.014）。对于危及器官（OARs），放射生物学加权的效果取决于所给予的剂量。当OARs的BT对D剂量的贡献<20Gy时，但BT方式是等效的。当BT对D的贡献≥20Gy时，HDR的OARs EQD2剂量均更高。
两种BT方式均能提供令人满意的靶体积覆盖，HDR技术对OARs D2的值略高，而中危临床靶体积在PDR计划中接受的剂量更高。当BT对OARs的贡献剂量>20Gy时，PDR相对于HDR的放射生物学益处占主导。
