局部晚期宫颈癌CT图像引导下^192Ir三维腔内后装治疗剂量体积参数与疗效关系

The correlation between DVH at CT-image based 192Ir intracavitary brachytherapy and effects or complications for patients with locally advanced cervical cancer

目的 观察CT图像引导下^192Ir三维腔内后装治疗的肿瘤靶区及危及器官受照射体积剂量参数与肿瘤局部控制率及晚期副反应之间关系.方法 10例局部晚期宫颈癌患者在完成盆腔外照射40 Gy及同期化疗后开始每周1次的CT图像引导下^192Ir三维腔内后装治疗,每次治疗前进行CT扫描定位,勾画肿瘤靶区（GTV、CTV）和危及器官,利用PLATO治疗计划系统进行逆向治疗计划设计及优化,CTV单次处方剂量为6 Gy,治疗5～7次.结果 1年盆腔控制率为90%,1～2级放射性肠炎发生率为50%,无≥3级副反应.90%CTV等效生物剂量（BED）和相当于2 Gy分次的等效剂量（EQD2）分别为（95.50±7.81）Gy和（79.73±6.57）Gy（α/β=10）.90%GTV的BED和EQD2分别为（101.86±7.27）Gy和（84.95±6.1）Gy（α/β=10）.90%处方剂量对GTV、CTV的覆盖率分别为92%±4%、87%±7%.直肠、乙状结肠2 cm^3体积受到的最小照射剂量分别为（74.97±1.64）、（67.93±4.30）Gy（EQD2,α/β=3）.与二维治疗计划相比,三维治疗计划在没有改变A点剂量、直肠参考点剂量情况下提高了GTV、CTV的90%体积受照射剂量及90%处方剂量对GTV、CTV的覆盖率.结论 CT图像引导下192Ir三维腔内后装治疗提高了处方剂量对肿瘤靶区的覆盖率,1年盆腔控制率为90%且无严重副反应,远期疗效观察中.

Objective To investigate the correlation between dose volume histogram（DVH）of tumor targets and organs at risk（OAR）at CT-image based 192Ir brachytherapy and effects and complications for patients with locally advanced cervical cancer. Methods Ten patients with FIGO stage ⅢB cervical cancer received CT image-based 192Ir intracavitary brachytherapy after 54 Gy of three-dimentional four-field pelvic external beam radiotherapy and concurrent weekly cisplatin chemotherapy. Before each brachytherapy,CT images were acquired with applicators in place. Gross tumor volume（GTV）, clinical target volume （CTV）and OAR were contoured and inverse treatment planning was designed and optimized by using PLATO treatment planning system. Conventional two-dimensional plans were also designed for comparison.The total intracavitary brachytherapy dose was 30 -42 Gy in 5 -7 fractions. The patients were followed, and the local control and complications were analyzed. The biologically equivalent dose（BED）and biologically equivalent dose in 2 Gy fractions（BED2）for GTV, CTV and OAR were calculated. The minimum dose in the most irradiated tissue volume 2 cm3（D2 cm3）adjacent to the applicator of the sigmoid colon, rectum,bladder and small bowel was determined from the DVH. Results The 1-year local pelvic control rate was 90% and grade 1-2 late complication of sigmoid colon and rectum was 50%. No grade 3 or more complications developed. On CT-image based planning, the BED and BED2 to 90% of the CTV（D90）were 95.50 Gy ± 7. 81 Gy and 79. 73 Gy ± 6. 57 Gy. The BED and BED2 to 90% of the GTV（D90）were 101.86 Gy ± 7.27 Gy and 84. 95 Gy ± 6. 1 Gy. The volume enclosed by 90% of prescribed dose（V90）for GTV and CTV were 92% ±4% and 87% ±7% respectively. The D2cm3 for rectum and sigmoid colon were 74. 97 Gy ±1.64 Gy and 67. 93 Gy ± 4. 30 Gy（EQD2, α/β = 3）. Comparing with 2D brachytherapy plans , CT - image based planning has improved D90 and V90 for GTV and CTV with similar dose at point A and rectum reference point. Conclusions Computer tomography-image based 192Ir brachytherapy has resulted in the better dose distribution to the tumor targets with excellent tumor control and acceptable toxicity.