食管癌靶区剂量不均匀性提高在逆向调强计划中的应用

Application of dose heterogeneity in the target volume in intensity-modulated radiation therapy of esophageal cancer

目的探讨提高靶区剂量不均匀性在食管癌逆向调强计划中应用的优势。方法10例食管癌患者中，95％体积的计划靶区（PTV）接受60Gy处方剂量，脊髓最高剂量不超过45Gy，分别为每例患者设计2套5野放疗计划。严格限制靶区最大剂量在63Gy以内的调强计划（IMRThom）和放松靶区最大剂量的限制到69Gy的调强计划（IMRTinhom）。根据剂量体积直方图比较PTV剂量和相关危及器官的受量差异。结果与IMRThom相比，IMRTinhom增加了靶区最大剂量（t=-23．58，P=0．000）和不均匀指数（t=-11．06，P=0．000），同时提高了其最小剂量（t=-3．37，P=0．012）和平均剂量（t=-4．95，P=0．002），降低了肺组织V5（t=6．96，P=0．000）、V10（t=5．24，P=0．001）、V15（t=4．73，P=0．002）、‰（t=8．08，P=0．000）、％，（t=8．58，P=0．000）及平均肺剂量（t=7．28，P=0．000），两套计划心脏的平均剂量和脊髓的最大剂量比较差异均无统计学意义。结论提高食管癌靶区剂量不均匀性的调强放疗计划，对于靶区的剂量递增及肺组织在低剂量照射区域的保护，更具有优势。

Objective To investigate the advantage of the intensity-modulated radiotherapy treatment （IMRT） by allowing dose heterogeneity in the target volume in esophageal cancer treatment planning. Methods Two sets of 5-field IMRT planning were designed for 10 esophageal cancer patients upon the condition of appropriate clinical tolerance level with the prescription dose of 60 Gy to 95% of the planned target volume （PTV） and the maximum dose of 45 Gy to the spinal cord： the IMRT with rigid restriction of the maximum homogeneous dose to the PTV within 63 Gy prescribing a homogeneous close （IMRThom ） and the IMRT allowing dose heterogeneity by loosening the constraints on maximum close in the PTV to 69 Gy （IMRTinhom ）. Dosimetric comparison was conducted by using dose-volume histograms. Results Compared to IMRTsom, the minimum close （t = -3.37,P=0.012）, maximum dose （t = -23, 58,P =0. 000） , mean dose （t = -4.95,P =0. 002）, and heterogeneity index （t = - 11.06,P = 0. 000） in PTV of the IMRTinho,, were all significantly increased, and the values of V5 （t = 6.96, P = 0.000）, V10（ t = 5. 24 ,P = 0. O01） , V15 （ t = 4. 73 ,P = 0. O02 ） , V20 （ t = 8. 08 ,P = 0. 000 ） , V25（t=8.58, P = 0. 000） , and mean dose （ t = 7.28,P = 0. 000） of the normal lungs were all significantly lower. There were no significant differences in all the indexes for the mean dose to the heart and maximum dose to the spinal cord between these 2 set of planning. Conclusions The IMRT plan allowing dose heterogeneity in the PTV escalates the prescription dose and decreases the doses to the lungs.