Consequences of additional use of contrast-enhanced (18)F-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 GTV(CT), GTV(PET), GTV(PET-CT) and OARs in these different image sets as well as the uniformity of target dose were analysed. RESULTS: The mean non-CE GTV(CT), GTV(PET) and GTV(PET-CT) were 76.9 ± 47.8, 47.0 ± 40.2 and 44.5 ± 34.7 cm(3) (mean ± standard deviation), respectively. The non-CE GTV(PET-CT) was significantly smaller than the non-CE GTV(CT) (p < 0.001). The CE GTV(PET-CT) was significantly smaller than the CE GTV(CT) (p = 0.033). For both the non-CE GTV(CT) and the CE GTV(CT), the intestine V(40) (the percentage of the intestine volume irradiated by 40 Gy), intestine V(50), intestine D(max) (the mean maximum dose), cord D(max), left kidney V(30), right kidney V(30), left kidney D(mean) (the mean dose), right kidney D(mean) and liver V(30) 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 D(max) (p = 0.023) and right kidney D(mean) (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.