Comparison of computed tomography- and positron emission tomography-based radiotherapy planning in cholangiocarcinoma.
BACKGROUND
The aim of this study was to compare computed tomography (CT)- and positron emission tomography (PET)/CT-based gross tumor volume (GTV) delineation and its subsequent expansion to the planning target volume (PTV), and to analyze the resultant doses of 3-dimensional conformal radiotherapy (3D-CRT) to critical organs.


METHODS
15 patients with unresectable extrahepatic cholangiocarcinoma (EHCC) were enrolled into this study. PTVCT-based plans were initially made, and then PTVPET-CT-based plans were created using the same beam angles and isocenter. The dosimetric parameters analyzed included GTVCT, PTVCT, GTVPET-CT and PTVPET-CT. Prescribed and delivered radiation doses to target volumes and delineated organs at risk were also compared.


RESULTS
Mean GTV and PTV were significantly reduced in the PET/CT-based plan compared to the CT-based plan; the mean reductions of GTV and PTV were 28.7% and 15.2%, respectively. The mean value for GTVPET/GTVCT mismatch was 49.5 ± 28.9%, and that for GTVCT/GTVPET was 95.9 ± 19.5%. The mean value for PTVPET-CT/PTVCT mismatch was 21.9 ± 7.0% and that for PTVCT/PTVPET-CT was 39.1 ± 9.2%. Liver doses were significantly reduced (17.1%) in the PET/CT-based plan compared to the CT-based plan; the doses received by at least 30% and 50% of the liver were 30.0%, and 27.3%, respectively.


CONCLUSIONS
The potential benefit of PET/CT is the reduction in geographic misses and regional treatment failures associated with CT-based planning.
Department of Radiation Oncology, Baskent University Medical Faculty, Adana, Turkey.
Cem
C
Onal
Savas
S
Topuk
Ali F
AF
Yapar
Melek
M
Yavuz
Erkan
E
Topkan
Aydin
A
Yavuz
D000368:Aged; D001650:Bile Duct Neoplasms / Q000175:diagnosis* / Q000628:therapy*; D001653:Bile Ducts, Intrahepatic / Q000000981:diagnostic imaging / Q000528:radiation effects; D018281:Cholangiocarcinoma / Q000175:diagnosis* / Q000532:radiotherapy*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D049268:Positron-Emission Tomography / Q000379:methods*; D011874:Radiometry; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods*; D020266:Radiotherapy, Conformal / Q000379:methods; D061089:Radiotherapy, Image-Guided; D015203:Reproducibility of Results; D012189:Retrospective Studies; D012680:Sensitivity and Specificity; D014057:Tomography, X-Ray Computed / Q000379:methods*; D016896:Treatment Outcome