量化分析早期肺癌和寡转移癌立体定向消融放疗过程中瘤体变化规律

目的 精确测算肺肿瘤立体定向消融放疗(stereotactic ablative radiotherapy, SABR)过程中瘤体的变化规律,优化SABR计划。方法 2011年10月至2014年10月,采集在河南省肿瘤医院放疗科接受SABR的66例早期肺癌和寡转移癌患者(共71枚肿瘤)的定位CT和验证CT图像,以首次治疗前肿瘤体积为基线,分别测算分次间肿瘤体积变化,用广义估计方程分析瘤体变化趋势。等效生物剂量(BED)60 Gy时瘤体变化超过25%的患者修订放疗计划,比较原计划和修正计划危及器官的受照剂量。结果 49枚瘤体缩小,21枚增大,1枚无变化,治疗过程中肿瘤体积变化差异无统计学意义(P=0.281)。当接受照射的BED达60 Gy时,26枚肿瘤体积变化超过25%(21枚缩小,5枚增大)。比较其修正计划和原计划,体积缩小的21枚肿瘤的肺V₅、脊髓D_max和D_{1.2 cm³}、食管D_max和D_{5 cm³}、胸壁D_{30 cm³}差异均有统计学意义(t=3.139~11.939,P<0.05),体积增大的5枚肿瘤的肺V₅和V₂₀、脊髓D_max和D_{1.2 cm³}、食管D_max、胸壁D_{30 cm³}差异均有统计学意义(t=-10.436~-2.518,P<0.05)。结论 SABR过程中肺肿瘤体积变化较大时,及时修订靶区和治疗计划可能使患者受益。

Quantitative analysis for the interfractional volumetric changes of stereotactic ablative radiotherapy for early-stage or oligo-metastatic lung tumors

Objective To measure the volumetric changes precisely during stereotactic ablative radiotherapy for early-stage and oligo-metastatic lung tumors and optimize the treatment plan timely. Methods From October 2011 to October 2014, 66 patients with 71 early-stage or oligo-metastatic lung tumors received SABR. Median age was 66 years. To measure the volume of tumors, the verification images were registered before each treatment fraction with stimulation images by reference to bone structure. Tumors volume was measured by the first verification images, and were defined as the reference when evaluating the trend of tumors volume change during SABR treatment. Generalized estimated equations were used to analyze the trend of the change of tumors volume over time with several possible predictors. The primary plan (P-plan) was modified when the biological effective dose (BED) of a tumor reached 60 Gy and volume change reached 25%. The modified plan was named as M-plan. Paired t-test was used to compare the dose of organs at risk (OAR) between M-plan and P-plan. Results In 71 tumors, 49(69%) tumors showed volumetric shrinkage, 21(30%) tumors showed enlargement and 1 tumor showed invariance. Generalized estimated equation showed no statistical significance (P=0.281) for the volumetric shrinkage of lung tumors. M-plan was made in 26 tumors. Of these tumors, 21 tumors decreased over 25% and the result of paired t-test showed V₅ of lung, D_max and D_{1.2 cm³} of spinal cord, D_max and D_{5 cm³} of esophagus and D_{30 cm³} of chest wall were statistically different between two plans(t=3.139~11.939,P<0.05). 5 tumors enlarged over 25% and the result of paired t-test showed V₅ and V₂₀ of lung, D_max and D_{1.2 cm³} of spinal cord, D_max of esophagus and D_{30 cm³} of chest wall were statistically different between the two plans(t=-10.436--2.518,P<0.05). Conclusions Size of lung tumors changed dynamically during SABR, but it is unnecessary to modify treatment plans for all tumors. The tumors which showed obvious volumetric change may benefit from modifying treatment plans.