Serial Studies Of The Impact Of PET-CT On Precise Radiotherapy Planning For Non-small Cell Lung Cancer

Objective To determine the relationship between l8F FDG PET-CT determined tumor diameter and true pathologic tumor diameter and to validate the difference between FDG PET-CT imaging for delineating GTV for precise radiotherapy to non-small cell lung cancer.Material and Methods The 18F FDG PET/CT data of 24 patients with NSCLC were analyzed. Ten patients were performed PET-CT scan preoperatively. The tumor diameter at X(lateral), Y(ventro-dorsal) and Z(crano-caudal)axis on PET, CT images was measured, as was the pathologic diameter on gross specimen. These findings were compared. Fourteen patients receiving 3-dimensional conformal radiotherapy were performed PET-CT pre-therapy. The gross tumor volumes (GTV) were delineated on PET images and simulation CT images respectively. The GTVpet and GTVct were calculated and compared.Results There was no statistical difference among the diameter at X and Y axis on PET, CT images and pathologic specimen(P>0.05), but the diameter at Z axis was larger than pathologic diameter(P<0.01). The GTV defined by PET as 58.4cm3+62.4cm3(M=31.0cm3, 3.2cm3-205.9cm3) was smaller than that defined by CT as 68.4cm3+83.2cm3 (M=35.3cm3, 4.6cm3~316.0cm3) . But there was no statistical difference between GTVpet and GTVct (P=0.40) . In five patients,GTVpET was greater than GTVCT of 27.2% averagely (5%~63%). In nine patients, GTVPET was smaller than GTVCT of 62.5% averagely (6%~143%).Conclusions Some factors such as respiration must be taken into account as delineating target volume with PET-CT images. Fusion imaging with PET and CT might be synergic for the precise delineation of GTV for the patients with atelectasis and obstructive pneumonitis or mediastinal lymph node metastasis.