新辅助化疗对局部晚期鼻咽癌自适应放疗的影响

Impact of Neoadjuvant Chemotherapy in Local-advanced Nasopharyngeal Carcinoma with Adaptive Radiation Therapy

目的研究局部晚期鼻咽癌新辅助化疗前后肿瘤体积变化,对调强放疗鼻咽癌患者腮腺、脑干、脊髓等剂量分布的影响,进而明确新辅助化疗在自适应放疗中的影响。方法选取2014年5~9月期间15例福建省肿瘤医院收治的鼻咽癌患者,均接受新辅助化疗、同步放化疗,放疗采用调强放射治疗。治疗前和第2周期新辅助化疗结束2周后分别行定位CT扫描,分别进行靶区勾画。根据两次CT制定plan1和plan2,将plan1映射到化疗后CT上获得新的计划plan1',分别对比plan1、plan1'、plan2,分析其解剖学及剂量学分布改变。结果 2周期新辅助化疗结束,GTVnx(P=0.000)及GTVnd(P=0.000)平均体积均明显缩小。将plan1和plan1'对比,颈部转移淋巴结最大层面最短径≥3cm(N≥3cm)的患者,其腮腺的Dmean、D50剂量明显升高(P<0.05)。将plan1'和plan2对比,脊髓的Dmax、D1cc剂量降低,腮腺(N≥3cm)组Dmean、D50剂量明显降低(P<0.05)。将6例原发肿瘤靠近脑干的患者进行剂量分析发现,plan1'和plan2对比,脑干Dmax(P=0.001)及D1cc(P=0.038)均降低。结论新辅助化疗后鼻咽肿瘤体积明显缩小,减少放射治疗过程中的解剖学和剂量学分布改变,从而减少放疗过程中实际剂量分布与计划剂量分布的差异,有助于减少自适应放疗过程中修正治疗计划的次数。新辅助化疗有助于N≥3cm的鼻咽癌患者腮腺的保护,也可降低肿瘤靠近脑干患者的脑干损伤。

Objective To investigate how the shrinking gross tumor volumes after neoadjuvant chemotherapy of local - advanced nasopharyngeal carcinoma （NPC） patients impacted the dose distribution during the intensity modulated radiation therapy （IMRT） , and find out the meaning of the neoadjuvant chemotherapy in adaptive radiotherapy （ART）. Methods From May 2014 to September 2014, 15 patients with NPC （nasopharyngeal carcinoma） treated with TP （Paclitaxel and cisplatin） were included. Computed tomography （CT） scans were performed before treatment （ CT1 ） and 2 weeks after 2 cycles of neo - adjuvant chemotherapy （CT2）. The target volume such as GTVnx, GTVnd, CTV1, CTV2, CTVnd and organs at risk （OARs） were contoured based on the CT images. Planl and plan2 were based on CT1 and CT2, respectively. Planl＇was generated by applying the beam configurations of planl to the anatomy of CT2. The anatomic and dosimetric changes were measured by comparing the planl, planl＇and plan2 respectively. Results Significant volumetric changes of target volumes （ GTVnx and GTVnd） were observed after 2 cycles of neo - adjuvant chemotherapy. The volumes of GTVnx before and after chemotherapy were 58.92±33.59cm3 vs 32.47± 19.14cm3 （P = 0. 000） , the volumes of GTVnd were 31.71 ± 21.97cm3 vs 13.76± 11.07cm3 （ P = 0. 000）. Compared with planl, the Dmean and D50 of parotid （ N ≥ 3cm） in plan 1＇ increased （ P 〈 0.05 ）. In contrast with planl＇, plan2 showed doses of spinal cord （including Dmax and Dlce of cord） , parotid （patients who had metastatic cervical lymph nodes which were greater than 3cm in diameter, N ≥ 3cm） in replanning （P 〈 0.05 ）. Analysis of the dosimetric changes of brain stem of 6 locally advanced patients, found that the Dmax of brain stem reduced from 60.58 ≥ 2.91 Gy to 56.01 ≥ 2.01 Gy（ P = 0. 001 ） , and D1 cc reduced from 52.64 ≥2.03Gy to 49.72 ≥ 1.34Gy （ P = 0. 038 ）. Conclusion Neoadjuvant chemotherapy by TP could reduce the anatomic and dosimetric changes, which would lessen the deviation of actual and planned does distribution in the progress of IMRT, and the fre- quency of replanning, thus benefit the implementation of ART. For patients who had lymph nodes metastases （N ≥ 3cm） , neoadjuvant chemotherapy helped protecting parotid glands. While, neoadjuvant chemotherapy could also reduce the damage of brain stem to patients whose primary tumor were closed to stem.