Dosimetry Study Of3D-CRT And IMRT Radiotherapy For Early Glottic Cancer After Surgery

Objective: To compare the dosimetry difference between threedimensional conformal radiatherapy (3D-CRT) and intensity-modulatedradiotherapy (IMRT) for early glottic cancer（EGC） after surgery.Method： Eleven patients with early glottic cancer treated bypostoperative radiotherapy for the first time were selected during October2012to December2014.All patients were underwent computedtomography simulation, and the target and organs at risk (OARs) weredelineated on the CT image layer by layer.3D-CRT and IMRT planswere designed for each patient with the prescription dose of50Gy to60Gy,5fractions per week,2Gy per fraction and all the patients weretreated with a6-MV X-ray beam from a medical linear accelerator.Finally, we got the relevant dosimetric parameters from the dosevolume histogram(DVH) and then made the statistical analysis.Results: In the3D-CRT group and IMRT group，V90%，V95%，Dmin，Dmean，Dmax，D95，D5，CI and HI were97.21±3.47%and98.64±2.38%，95.45±4.68%and97.96±2.77%，2059.34±1857.70cGy and3033.52±1957.82cGy，5465.94±478.07cGy and5548.57±453.29cGy，5924.38±475.82cGy and5895.62±509.06cGy， 5895.62±509.06cGy and5023.16±677.29cGy，5825.56±465.38cGyand5738.56±499.31cGy，0.61±0.09and0.83±0.10，(1.15，0.18) and(1.09，0.06), respectively. V90%，V95%，Dmin，Dmean and Dmax of3D-CRT group were all slight lower than the corresponding parameters inthe IMRT group, while there were no significant differencesstatistically(P>0.05).D5in the3D-CRT group was little higher thanIMRT group, while there were no significant differences statistically(P>0.05).D95and HI in the3D-CRT group were higher than thecorresponding parameters in the IMRT group，and the differences weresignificant statistically(P <0.05).CI in the3D-CRT group was lower thanthat in the IMRT group， and the differences were significantstatistically(P <0.05).Dmean and Dmax of spinal cord PRV in the3D-CRT group were208.77±99.60cGy and2150.56±998.20cGy，whichwere lower than1171.60±733.60cGy and3274.51±376.68cGy in theIMRT group，and the differences were significant statistically（P＜0.05）.Conclusions: IMRT has more significant advantages on targetconformal degree and uniformity of the dose distribution than3D-CRT，but is not as good as3D-CRT in protecting the spinal cord.