Impact of PET/CT on dosimetric parameters of three-dimensional conformal radiotherapy planning in patients with non-small cell lung cancer

OBJECTIVE: To investigate the impact of PET/CT on three-dimensional conformal radiotherapy(3D-CRT) planning of non-small cell lung cancer(NSCLC).METHODS: PET/CT scanning was performed in 83 pathologically proven NSCLC patients for radical radiotherapy.The gross tumor volume(GTV) was delineated on the CT images(GTVCT) alone and then coregestered CT and 18F-FDG-PET data(GTVPET/CT).For each patient,two three-dimensional conformal radiotherapy plans were made: one with a CT-based target volume and one with a PET/CT-based target volume.From the dose-volume histograms and dose distributions on each plan,the dosimetric factors were analyzed and compared.RESULTS: PET/CT clearly altered the radiation therapy volume in 44(53.01%,44/83) cases,while 31 with the reduction of planning target volume(PTV) and/or GTV,and 13 with the enlargement.Between the PET/CT and CT radiotherapy planning,the difference of volume of GTV(VGTV) and dosimetric parameters including esophageal volume receiving at least 50 Gy(VE50),the maximum dose of spinal cord receiving(SCM) and the maximum dose of esophagus receiving(ESM) were statistically significant(P were 0.001,0.001,0.000 and 0.002).CONCLUSION: The incorporation of 18F-FDG-PET information in CT-based radiotherapy planning reduced the radiation exposure of the esophagus and spinal cord,and thus allowed significant radiation dose escalation while respecting all relevant normal tissue constraints.