Consequences of additional use of contrast-enhanced 18F-FDG PET/CT in target volume delineation and dose distribution for pancreatic cancer

OBJECTIVE To compare the differences between contrast-enhanced (CE) fluorine-18 fludeoxyglucose ((18)F-FDG) positron emission tomography (PET)/CT and CECT in target volume delineation and radiotherapy (RT) dose distribution, and to evaluate the sparing of organs at risk (OARs) in the treatment plan of locally advanced pancreatic cancer (LAPC). METHODS 21 consecutive patients with LAPC with histologically or cytologically confirmed adenocarcinoma underwent both non-CECT and (18)F-FDG scans; 11 of whom also underwent CECT scans. Intensity-modulated RT plans (prescribed dose, 54 Gy) were constructed to cover the corresponding gross tumour volume (GTV). The differences among GTVCT, GTVPET, GTVPET-CT and OARs in these different image sets as well as the uniformity of target dose were analysed. RESULTS The mean non-CE GTVCT, GTVPET and GTVPET-CT were 76.9 ± 47.8, 47.0 ± 40.2 and 44.5 ± 34.7 cm(3) (mean ± standard deviation), respectively. The non-CE GTVPET-CT was significantly smaller than the non-CE GTVCT (p < 0.001). The CE GTVPET-CT was significantly smaller than the CE GTVCT (p = 0.033). For both the non-CE GTVCT and the CE GTVCT, the intestine V40 (the percentage of the intestine volume irradiated by 40 Gy), intestine V50, intestine Dmax (the mean maximum dose), cord Dmax, left kidney V30, right kidney V30, left kidney Dmean (the mean dose), right kidney Dmean and liver V30 were 5.90%, 2.52%, 5500 cGy, 2194 cGy, 3.40%, 0.68%, 747 cGy, 550 cGy and 5.37%, respectively. There are significant differences between the non-CE CT and the non-CE PET-CT in intestine Dmax (p = 0.023) and right kidney Dmean (p = 0.029). CONCLUSION Co-registration of (18)F-FDG PET with CECT may improve the accuracy of GTV delineation in LAPC and might reduce the adverse effect of irradiation. ADVANCES IN KNOWLEDGE Individual adaptation of RT based on functional CE (18)F-FDG PET/CT imaging is possible and highly promising in LAPC.