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| Prediction of PET/CT to Alleviate Radiation Pneumonitis in Patients with Non-small Cell Lung Cancer for 3-dimentional Confo rmal Radiotherapy |
| GONG He-yi, YU Jin-ming, LI Jian-bin, et al |
| Shandong Tumor Hospital, Jinan 250117, China |
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Abstract Objective To investigate the impact of PET/CT on clinical staging of non-small cell lung cancer (NSCLC),delineation of target volume,and prediction to alleviate radiation pneumonitis (RP) from 3-dimentional conformal radiotherapy (3D-CRT) planning.Methods From October 2002 to June 2004,34 patients diagnosed cytologically or pathologically with NSCLC,who were candidates for radical radiotherapy or surgery,received PET/CT scanning.Both images were transmitted into treatment planning system (TPS) workstations respectively and were fused and reconstructed.All patients were staged according to the 1997 World Health Organization (WHO) staging system.The impact of PET/CT on the clinical staging of all the patients was determined.The gross tumor volume (GTV) was delineated on the CT imaging and PET/CT fused imaging respectively.Based on the two images,3D-CRT planning was made respectively at the TPS workstation with Topslane software,the planning target volumes (PTV) being defined with a 15 mm margin around GTV of primary lumps (PTV1) and 7 mm for involved lymph nodes (PTV2).Evaluating indexes including VPTV (volume of PTV,VPTV=VPTV1+VPTV2),V20(percentage of the total lung volume receiving more than 20 Gy),MLD (mean lung dose),TCP (tumor control probability),NTCP (normal tissue complication probability),and Ds (dose to spinal cord) were selected to be paralleled to compare the quality of the two plans and the impact of PET/CT on RP was further analyzed.Results In 13 of 34(38.2%) cases,PET/CT information changed the clinical staging,8 of which were upstaged and 5 downstaged.For 10 of 34(29.4%) cases,PET/CT results modified their management decisions.Among 16 patients performed by surgery,14 had consistent PET/CT staging with pathologic staging.The sensitivity of PET/CT was 93.3% and accuracy 87.5%.Difference of indexes including VPTV,V20 and MLD between the two radiation planning was statistically significant,but Ds,TCP and NTCP were not statistically different.Conclusion PET/CT has notable impact on clinical staging,target volume delineation and hence on its 3D-CRT planning of NSCLC.In contouring the target volume,compared with CT imaging,PET/CT can decrease VPTV,V20 and MLD significantly in patients with atelectasis and obstructive pneunonitis,so can reduce the rate and severity of RP effectively and can better protect normal lung tissues.
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Received: 28 January 2005
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