鼻咽癌放疗中肿瘤退缩变化对大体肿瘤靶区的影响

The effect of tumor regression during radiotherapy on gross tumor volume in patients with nasopharyngeal carcinoma

摘要:

目的 探讨鼻咽癌放疗中肿瘤退缩变化对大体肿瘤靶区的影响及调整放疗计划的必要性。方法 收集确诊的鼻咽癌患者52例，其中T1期5例、T2期17例、T3期19例和T4期11例。所有患者均接受放/化疗综合治疗。患者在放疗前及放疗疗程中的第20、22次分别进行1次放疗定位CT扫描。分别在2次定位CT扫描的图像上勾画GTV靶区，在Pinnacle计划系统内将前后2次CT扫描的图像及勾画的靶区进行匹配、融合，然后逐层比较前后2次勾画的GTV靶区的重合度，分别找出GTV靶区在前界、后界、左侧界及右侧界偏差最大的层面，测量并记录最大位移距离。按照肿瘤T分期将患者分为T1、T2、T3及T4共4组进行统计学分析。结果 放疗后GTV靶区在前、后及两侧界等4个边界上的退缩程度不同，在肿瘤前界上产生的最大位移距离最大，其中以T4期最大，为（4.7±1.2） mm，其后依次为后界、左右侧界。将所测量到的各个边界在不同T分期肿瘤中的最大位移距离分别进行方差分析，结果显示，后界、左右侧界的最大位移距离在不同T分期肿瘤中的差别具有统计学意义（F值分别为：17.26、19.35、3.51；P值分别为：0.001、0.001、0.03），但前界的最大位移距离在不同T分期肿瘤中的差别无统计学意义（F=0.73，P=1.05）。结论 不同T分期肿瘤在4个边界上的退缩程度不同；当治疗前影像提示咽旁隙仅肿瘤压迫而非侵犯时及T4期肿瘤侵犯颅内时，放疗期间由于肿瘤的退缩，及时修改治疗计划非常必要，这样对于更好地保护正常组织器官功能有重要意义。

Abstract:

Objective To investigate the effect of tumor regression during radiotherapy on gross tumor volume (GTV) in patients with nasopharyngeal carcinoma (NPC) and the necessity of adjusting radiotherapy plan. Methods total of 52 patients with newly diagnosed NPC were collected. As for the T stage, 5 cases belonged to T1, 17 to T2, 19 to T3 and 11 to T4. All patients were treated with intensity modulated radiation therapy (IMRT) plus chemotherapy. Patients underwent radiotherapy localization CT scans before receiving radiotherapy and between the 20th and 22nd sessions during radiotherapy. The GTVs were delineated on the images of two localized CT scans correspondingly. The images and their outlined target volumes were matched and merged in the Pinnacle planning system. The coincidences of the GTVs between the two scans were then compared level-by-level. The levels with the largest deviations in the anterior, posterior and bilateral boundaries were found with measurement and record of the maximum displacement distances. Statistical analyses were performed among groups with different T stage. Results During radiotherapy, the degrees of regression in GTV of NPC were different on four boundaries. The GTV regression generated the largest displacement distance on the anterior boundary, especially in those of T4 stage with the largest distance of (4.7±1.2) mm, followed by the posterior boundary and bilateral boundaries. Variance analyses conducted on the maximum displacement distance of each boundary in different T stages showed that the differences of the maximum displacement distance of the posterior boundary and bilateral boundaries among different T stages were statistically significant (F=17.26, 19.35, 3.51 and P=0.001, 0.001, 0.03 respectively), but the difference in anterior boundary was statistically insignificant (F=0.73,P=1.05). Conclusions The tumors with different T stage have different degrees of regression on the four boundaries. In NPC patients with parapharyngeal space tumor compression rather than invasion, T4 stage with intracranial invasion before radiotherapy, it is necessary to modify the treatment plan during radiotherapy in time so as to protect the function of normal tissues and organs preferably.