Prins Fieke M, van der Velden Joanne M, Gerlich Anne S, Kotte Alexis N T J, Eppinga Wietse S C, Kasperts Nicolien, Verlaan Jorrit J, Pameijer Frank A, Kerkmeijer Linda G W
Department of Radiation Oncology, University Medical Center Utrecht, Utrecht, the Netherlands.
Department of Orthopedic Surgery, University Medical Center Utrecht, Utrecht, the Netherlands.
Ann Palliat Med. 2017 Dec;6(Suppl 2):S147-S154. doi: 10.21037/apm.2017.06.07. Epub 2017 Jul 11.
In metastatic renal cell carcinoma (mRCC) there has been a treatment shift towards targeted therapy, which has resulted in improved overall survival. Therefore, there is a need for better local control of the tumor and its metastases. Image-guided stereotactic body radiotherapy (SBRT) in bone metastases provides improved symptom palliation and local control. With the use of SBRT there is a need for accurate target delineation. The hypothesis is that MRI allows for better visualization of the extend of bone metastases in mRCC and will optimize the accuracy of tumor delineation for stereotactic radiotherapy purposes, compared with CT only.
From 2013 to 2016, patients who underwent SBRT for RCC bone metastases were included. A planning CT and MRI were performed in radiotherapy treatment position. Gross tumor volumes (GTV) in both CT and MRI were delineated. Contouring was performed by a radiation oncologist specialized in bone metastases and verified by a radiologist, based on local consensus contouring guidelines. In both CT and MRI, the GTV volumes, conformity index (CI) and distance between the centers of mass (dCOM) were compared.
Nine patients with 11 RCC bone metastases were included. The GTV volume as defined on MRI was in all cases larger or at least as large as the GTV volume on CT. The median GTV volume on MRI was 33.4 mL (range 0.2-247.6 mL), compared to 18.1 mL on CT (range 0.1-195.9) (P=0.013).
Contouring of RCC bone metastases on MRI resulted in clinically relevant and statistically significant larger lesions (mean increase 41%) compared with CT. MRI seems to represent the extend of the GTV in RCC bone metastases more accurately. Contouring based on CT-only could result in an underestimation of the actual tumor volume, which may cause underdosage of the GTV in SBRT treatment plans.
在转移性肾细胞癌（mRCC）中，治疗已转向靶向治疗，这使总生存期得到改善。因此，需要更好地对肿瘤及其转移灶进行局部控制。骨转移瘤的影像引导立体定向体部放疗（SBRT）可改善症状缓解和局部控制。使用SBRT时需要准确勾画靶区。假设是，与仅使用CT相比，MRI能更好地显示mRCC骨转移灶的范围，并将优化立体定向放疗的肿瘤勾画准确性。
纳入2013年至2016年接受SBRT治疗RCC骨转移瘤的患者。在放疗治疗体位进行计划CT和MRI检查。在CT和MRI上均勾画大体肿瘤体积（GTV）。由一名专门从事骨转移瘤治疗的放射肿瘤学家进行轮廓勾画，并由一名放射科医生根据局部共识轮廓勾画指南进行核实。比较CT和MRI上的GTV体积、适形指数（CI）和质心之间的距离（dCOM）。
纳入9例有11个RCC骨转移灶的患者。MRI上定义的GTV体积在所有病例中均大于或至少与CT上的GTV体积一样大。MRI上的GTV体积中位数为33.4 mL（范围0.2 - 247.6 mL），而CT上为18.1 mL（范围0.1 - 195.9）（P = 0.013）。
与CT相比，在MRI上勾画RCC骨转移灶导致临床上相关且在统计学上有显著意义的更大病变（平均增加41%）。MRI似乎更准确地显示了RCC骨转移灶中GTV的范围。仅基于CT的轮廓勾画可能会导致对实际肿瘤体积的低估，这可能会导致SBRT治疗计划中GTV剂量不足。
