Dosimetric Research Of CF-IMRT And SIB-IMRT In Limited Stage Small Cell Lung Cancer

Objective:To evaluate the dosimetric features of CF-IMRT and SIB-IMRT in limited stage small cell lung cancer(LS-SCLC),and provides reference for clincal practice.Materials and methods:A total of 11 patients with LS-SCLC were studied.The patients were scanned by CT and their target volumes and organs at risk were delineated.PGTV and PTV were defined as GTV and CTV plus 5~8 mm in all directions.CF-IMRT(PGTV 54 Gy/27 f,PTV 40 Gy/20 f)and SIB-IMRT(PGTV 54 Gy/20 f,PTV 40 Gy/20 f)plans were made for every patients and dosimetric parameters of target volumes and organs at risk were compared between two plans.Results:Those of CF-IMRT plan were significantly lower than the PTV-D5(P = 0.005)and PGTV-D5(P = 0.003)of SIB-IMRT plan.But there not were differences in the PTV-D95(P = 0.456)and PGTV-D95(P = 0.191)between SIB-IMRT and CF-IMRT plans.The PTV and PGTV conformal indexes(CI)of CF-IMRT plan were 0.40 ± 0.06 and 0.50 ± 0.1 respectively,and those of SIB-IMRT plan were 0.44 ± 0.06 and 0.63 ± 0.06 respectively,so CF-IMRT plan was significantly inferior to SIBIMRT plan(P = 0.047,P < 0.001).The PTV and PGTV heterogeneity indexes(HI)of CF-IMRT plan were 1.38 ± 0.02 and 1.05 ± 0.01 respectively,and those of SIB-IMRT plan were 1.42 ± 0.02 and 1.09 ± 0.02 respectively,so CF-IMRT plan was significantly better than SIBIMRT plan(P = 0.001,P < 0.001).The heart V30 and V40 of CF-IMRT plan were significantly higher than SIB-IMRT plan(P = 0.013,P = 0.005,respectively).As compared with those of CF-IMRT plan,the mean lung dose(MLD),and V5,V20,V30,V40 and V45 of lung of SIB-IMRT plan all decreased significantly(P < 0.05).There not were differences in the V5,V20,V30 and V40 of esophagus between two plans(P > 0.05),but esophagus V45 and mean esophageal dose of CF-IMRT plan was significantly higher than that of SIB-IMRT plan(P = 0.004,P = 0.023,respectively).The difference of maximum dose for spinal cord between two plans was not statistically significant(P = 0.904).Conclusion1.As compared with CF-IMRT plan,SIB-IMRT plan achieved better conformal index(CI),its dose distribution was closed to target volume.2.As compared with CF-IMRT plan,SIB-IMRT plan showed the advantages in the protection of lung,esophagus and heart.There was no difference in the spinal cord maximum doses between the two plans.3.As compared with CF-IMRT plan,SIB-IMRT plan increased biologically effective dose(BED)and shortened treatment time.