Radiation Medicine Program, Princess Margaret Cancer Centre/University Health Network, Toronto, Canada.
Radiother Oncol. 2013 Apr;107(1):46-51. doi: 10.1016/j.radonc.2013.02.012. Epub 2013 Mar 27.
To analyze systematic changes in tumor and normal tissue anatomy and dosimetry using serial MR imaging during pulsed dose rate brachytherapy (PDR BT) for cervical cancer.
Forty-three patients with cervical cancer underwent MR-guided PDR BT using an intrauterine applicator alone after external beam radiotherapy. MR imaging was repeated on days 2 and 3 of treatment and the day 1 plan was applied to the re-contoured volumes.
The mean uterine volume and mean HR CTV increased during treatment. This resulted in a decrease in the mean HR CTV D90 relative to the day 1 planned dose. There was no change in the mean bladder volume during treatment but the mean rectal volume increased. This correlated with an increase in the mean rectal dose. There were four local recurrences. There was no apparent relationship between either the planned or the delivered HR CTV D90 and local recurrence. There was only one case of late bladder toxicity but nine patients developed late rectal toxicity. The cumulative rectal dose during treatment was a better predictor of late rectal toxicity than the planned dose.
Significant changes in tumor and normal tissue anatomy and dosimetry can occur during PDR BT and should be tracked and corrected using serial imaging and plan adaptation, especially when the day 1 tumor or normal tissue doses are close to the planning constraints.
本研究旨在通过对宫颈癌患者进行脉冲剂量率近距离放疗（PDR BT）时的系列磁共振成像（MR）分析，研究肿瘤和正常组织解剖结构及剂量学的系统变化。
43 例宫颈癌患者在接受外照射放疗后单独使用宫内施源器进行了 MR 引导的 PDR BT。治疗第 2 天和第 3 天重复进行 MR 成像，将重新勾画的体积应用于第 1 天的计划。
治疗过程中，子宫体积和 HR CTV 平均体积逐渐增大，导致 HR CTV D90 相对于第 1 天计划剂量降低。治疗过程中膀胱平均体积无变化，但直肠平均体积增大，直肠平均剂量相应增加。4 例患者局部复发。无论是计划剂量还是实际剂量 HR CTV D90 与局部复发均无明显关系。仅有 1 例发生晚期膀胱毒性，9 例发生晚期直肠毒性。治疗过程中的累积直肠剂量比计划剂量更能预测晚期直肠毒性。
PDR BT 过程中肿瘤和正常组织解剖结构及剂量学变化显著，应通过连续成像和计划调整进行跟踪和校正，尤其是在第 1 天肿瘤或正常组织剂量接近计划限制时。
