Department of Radiation Oncology, University of Texas Southwestern Medical Center, Dallas, TX; Innovation Technology of Radiotherapy Computation and Hardware (iTORCH) Lab, University of Texas Southwestern Medical Center, Dallas, TX.
Department of Radiation Oncology, University of Texas Southwestern Medical Center, Dallas, TX.
Brachytherapy. 2021 Jan-Feb;20(1):136-145. doi: 10.1016/j.brachy.2020.09.004. Epub 2020 Oct 29.
The purpose of this study is to compare the predicted rate of local control and bladder and rectum toxicity rates for image-guided adaptive brachytherapy plans using a tandem and ovoid (T/O) applicator versus using a simulated hybrid intracavitary/interstitial tandem and ring applicator with needles (T/R + N) for patients with locally advanced cervical cancer (LACC).
Patients with ≥ FIGO Stage IIB locally advanced cervical cancer treated with T/O from a single institution were included. Simulated treatment plans were created with a T/R + N applicator for the best high-risk clinical target volume (CTV) coverage and minimal dose to organs at risk. Three-year local control rate was estimated using published dose-volume effect relationships. Next, the high-risk CTV EQD2 D90 of T/R + N plans were calculated, and bladder and rectum toxicity rates were estimated. Analysis was performed in subpatient groups defined based on tumor volume and ratio of maximal and minimal tumor radii (RR) that reflects tumor shape asymmetry.
Improvements in predicted local control rate for the T/R + N were 0.8, 4.1, 1.6, and 3.9% for groups with tumor volume <35 cc, ≥35 cc, RR < 2.0, and ≥2.0, respectively, with the latter three being statistically significant. Predicted reductions in Grade 2-4 toxicity rates of bladder and rectum were significant in all groups except bladder toxicity in tumor volume <35 cc, when T/R + N plans were normalized to the same CTV coverage as the T/O plans. Comparing unnormalized T/R + N plans and T/O plans, predicted toxicity reductions were significant in all groups except rectum toxicity in RR ≥ 2.0. Predicted reduction of toxicity rate was larger for patients with large tumor or large tumor RR, although some reductions were relatively small.
Cases with large tumor (volume ≥35 cc) or large tumor asymmetry (RR ≥ 2.0) would probably benefit more from the use of hybrid applicators.
本研究旨在比较使用 T/O 施源器和模拟的 T/R+N 施源器（带针）治疗局部晚期宫颈癌（LACC）患者的图像引导自适应近距离治疗计划的局部控制率和膀胱、直肠毒性发生率。
纳入了在单中心接受 T/O 治疗的≥FIGO 分期 IIB 局部晚期宫颈癌患者。使用 T/R+N 施源器创建了模拟治疗计划，以实现最佳高危临床靶区（CTV）覆盖和最小危及器官剂量。使用已发表的剂量-体积效应关系估计 3 年局部控制率。然后，计算 T/R+N 计划的高危 CTV EQD2 D90，估计膀胱和直肠毒性发生率。根据肿瘤体积和最大最小肿瘤半径比（RR）对亚患者组进行分析，RR 反映肿瘤形状的不对称性。
对于肿瘤体积<35 cc、≥35 cc、RR<2.0 和≥2.0 的患者组，T/R+N 计划预测的局部控制率提高了 0.8%、4.1%、1.6%和 3.9%，后三组具有统计学意义。除肿瘤体积<35 cc 组的膀胱毒性外，所有组的膀胱和直肠 2-4 级毒性发生率预测降低均具有统计学意义，当 T/R+N 计划的 CTV 覆盖与 T/O 计划相同时。与 T/O 计划相比，在所有组中，除 RR≥2.0 组的直肠毒性外，未归一化的 T/R+N 计划和 T/O 计划预测的毒性降低均具有统计学意义。对于肿瘤较大或肿瘤 RR 较大的患者，预测毒性降低较大，尽管有些降低相对较小。
对于肿瘤较大（体积≥35 cc）或肿瘤不对称性较大（RR≥2.0）的患者，使用混合施源器可能会获益更多。
