Kissel Manon, Fournier-Bidoz Nathalie, Henry Olivier, Bockel Sophie, Kumar Tamizhanban, Espenel Sophie, Chargari Cyrus
Radiation Therapy Department, Gustave Roussy, Villejuif, France.
Medical Physics Department, Gustave Roussy, Villejuif, France.
J Contemp Brachytherapy. 2021 Feb;13(1):24-31. doi: 10.5114/jcb.2021.103583. Epub 2021 Feb 18.
Residual distal parametrial involvement after radiochemotherapy is a true challenge for brachytherapists since the width and asymmetry of high-risk clinical target volume (HR-CTV) are difficult to cover properly with a standard implant.
Dosimetric plans of five patients treated with Venezia advanced gynecological applicator at our institution were reviewed. For each patient, we compared the original plan with a new plan where oblique needles were removed and re-optimized manually. Optimization process was halted when EQD2 D HR-CTV reached 90 Gy, when one hard constraint to organs at risk (OARs) was reached according to the EMBRACE II protocol, or when dose-rate of one of OARs exceeded 0.6 Gy/h.
Tumors were large; median HR-CTV volume was 64 cc and median distance between tandem and outer contour of HR-CTV was 40 mm. For the five patients, HR-CTV EQD2 D was superior in the plan using oblique needles, with a median difference of 6.5 Gy (range, 1.7-8.5 Gy). Median D HR-CTV and intermediate-risk CTV (IR-CTV) were significantly increased with oblique needles: 85.9 Gy (range, 83.2-90.3 Gy) vs. 81.5 Gy (range, 77.4-84 Gy), and 68.7 Gy (range, 66.3-72.3 Gy) vs. 67 Gy (range, 64.3-69.1 Gy), = 0.006 for both. There were no significant differences in the dose to OARs. Plans with only parallel needles had less favorable dose distribution, with cold spots on the outer parametria and higher vaginal activation to compensate parametrial coverage in its inferior part.
Venezia applicator permits reproducible application to increase CTV coverage in patients with distal parametrial tumor residue during brachytherapy, while maintaining acceptable dose to OARs.
放化疗后残留的远端宫旁组织受累对近距离放疗医生来说是一项真正的挑战，因为高危临床靶区（HR-CTV）的宽度和不对称性难以通过标准植入物妥善覆盖。
回顾了我院使用威尼斯先进妇科施源器治疗的5例患者的剂量计划。对于每位患者，我们将原始计划与一个新计划进行比较，在新计划中移除了斜针并手动重新优化。当EQD2 D HR-CTV达到90 Gy、根据EMBRACE II协议达到对危及器官（OARs）的一项硬约束或当其中一个OARs的剂量率超过0.6 Gy/h时，优化过程停止。
肿瘤体积较大；HR-CTV体积中位数为64 cc，串联与HR-CTV外轮廓之间的距离中位数为40 mm。对于这5例患者，使用斜针的计划中HR-CTV EQD2 D更高，中位数差异为6.5 Gy（范围为1.7 - 8.5 Gy）。使用斜针时，HR-CTV的D中位数和中危CTV（IR-CTV）显著增加：85.9 Gy（范围为83.2 - 90.3 Gy）对81.5 Gy（范围为77.4 - 84 Gy），以及68.7 Gy（范围为66.3 - 72.3 Gy）对67 Gy（范围为64.3 - 69.1 Gy），两者均为P = 0.006。对OARs的剂量无显著差异。仅使用平行针的计划剂量分布较差，宫旁外侧有冷点，且阴道激活更高以补偿其下部宫旁组织的覆盖。
威尼斯施源器允许可重复应用，以增加近距离放疗期间远端宫旁肿瘤残留患者的CTV覆盖，同时保持对OARs的可接受剂量。
