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目的:比较局部晚期鼻咽癌同期加量(simultaneous integrated boost conformal radiotherapy,SIB-CRT)与传统后期颅底加量适形放疗技术(traditional later skull base boost technique,LB-CRT)生物等效剂量(biologically effective dose,BED)的分布差异,探讨生物剂量概念对临床应用的影响。方法:选取2012-09-12-2012-12-19在中山大学肿瘤防治中心初治的10例鼻咽癌患者,在设计分段照射70Gy常规计划的基础上,每例患者均对生物加量靶区分别设计SIB-CRT及LB-CRT 2种计划,用剂量体积直方图比较2种技术在靶区及危及器官中的物理剂量学差异,并采用L-Q模型将其转换成BED进行比较。结果:物理剂量方面,2种照射技术的计划靶体积(planning target volume,PTV)中,PTV2和PTV1的剂量分布差异无统计学意义;但SIB-CRT中PTV-G的95%处方剂量所包含靶体积百分数(V95%)为99.3%,优于LB-CRT的98.6%,P=0.005;SIB-CRT中PTV-B的V95%为97.1%,明显优于LB-CRT的48.3%,P=0.001;SIB-CRT在PTV-B的最小剂量(Dmin)为(70.2±2.1)Gy,优于LB-CRT的(68.5±3.3)Gy,提高2.48%,P=0.010;SIB-CRT在PTV-B的最大剂量(Dmax)为(77.0±1.8)Gy,优于LB-CRT的(75.6±1.1)Gy,提高1.85%,P=0.016;SIB-CRT在PTV-B的平均剂量(Dmean)为(74.2±0.8)Gy,优于LB-CRT的(72.5±1.3)Gy,提高2.34%,P=0.015。SIB-CRT较LB-CRT同侧颞颌关节Dmean减少了4.8%,50%体积所受最大剂量(D50)减少了5.1%,P值均为0.001;对侧则相应减少了5.9%和6.0%,P值均为0.007。生物学剂量方面,SIB-CRT物理处方剂量较LB-CRT低约1Gy,但两者在PTV-B的Dmin、Dmax及Dmean的BED差异增大,SIB-CRT的Dmin为87.9Gy,优于LB-CRT的85.2Gy,提高3.17%,P=0.010;SIB-CRT的Dmax为98.6Gy,优于LB-CRT的94.4Gy,提高4.45%,P=0.001;SIB-CRT的Dmean为93.8Gy,优于LB-CRT的89.8Gy,提高4.45%,P=0.001。校准后物理剂量(adjusted physical dose,APD)与BED较一致,分别提高3.08%、4.23%及4.60%。SIB-CRT中PTV-G的105%与95%等剂量曲线间物理剂量差异为10.5%,BED差异增大,达22.1%,而APD差异为13.7%,反映生物特性的差异不如BED。结论:SIB-CRT技术更加适形和精确,且不明显增加甚至可减少部分危及器官的照射。应用BED对不同分割剂量及次数的放疗方案之间生物效应进行量化评估是可行的。
Objectives: To compare the bioequivalent dose-response of SIB-CRT with traditional late skull base boost technique (LB-CRT) biologically effective dose, BED) to explore the impact of the concept of biological dose on clinical application. Methods: Select 2012-09-12 2012-12-19 10 cases of nasopharyngeal carcinoma patients who were initially treated at Sun Yat-sen University Cancer Center, based on the design of 70Gy routine plan, each patient added to the biological Target areas were designed SIB-CRT and LB-CRT two kinds of plans, the use of dose-volume histogram to compare the two technologies in the target area and the organ at risk of physical dose differences, and using the LQ model converted to BED for comparison. RESULTS: There was no statistically significant difference in the dose distribution between PTV2 and PTV1 in the planning target volume (PTV) of the two irradiation technologies in terms of physical dose; however, the 95% prescribed dose of PTV-G in SIB-CRT included The target volume percentage (V95%) was 99.3%, superior to 98.6% of LB-CRT with P = 0.005; V95% of PTV-B in SIB-CRT was 97.1%, significantly better than that of LB-CRT 48.3% 0.001). The minimum dose of SIB-CRT at PTV-B was (70.2 ± 2.1) Gy, which was 2.48% better than that of LB-CRT at 68.5 ± 3.3 Gy The maximum dose (Dmax) of B was (77.0 ± 1.8) Gy, which was superior to that of LB-CRT (75.6 ± 1.1) Gy by 1.85%, P = 0.016. The average dose of SIB-CRT at PTV-B (74.2 ± 0.8) Gy better than (72.5 ± 1.3) Gy LB-CRT, an increase of 2.34%, P = 0.015. SIB-CRT decreased by 4.8% compared with LB-CRT ipsilateral temporomandibular joint Dmean, and the maximum dose (D50) of 50% volume decreased by 5.1%, P value was 0.001; contralateral was reduced by 5.9% and 6.0% , P values were 0.007. Physiological dose of SIB-CRT was about 1 Gy lower than that of LB-CRT in biological dosage, but BED difference between Dmin, Dmax and Dmean in PTV-B increased, Dmin in SIB-CRT was 87.9Gy, The Dmax of SIB-CRT was 98.6 Gy, which was 4.45% better than that of LB-CRT, P = 0.001; the Dmean of SIB-CRT was 93.8 Gy, which was superior to that of LB-CRT 89.8 Gy for LB-CRT, 4.45% increase, P = 0.001. Adjusted physical dose (adjusted physical dose, APD) and BED are more consistent, increased by 3.08%, 4.23% and 4.60%. The difference in the physical dose between the 105% and 95% isodose curves of PTV-G in SIB-CRT was 10.5%, the BED difference increased to 22.1%, and the APD difference was 13.7%, reflecting the difference in biological characteristics as BED. Conclusion: The SIB-CRT technology is more conformal and accurate, with no significant increase or even partial reduction of organ-exposure. It is feasible to use BED to quantitatively evaluate the biological effects of radiotherapy regimens with different doses and times.