Value of combined PET/CT for radiation planning in CT-guided percutaneous interstitial high-dose-rate single-fraction brachytherapy for colorectal liver metastases.
OBJECTIVE
To determine the additional value of fluorodeoxyglucose-positron emission tomography (PET) for clinical target volume definition in the planning of computed tomography (CT)-guided interstitial brachytherapy for liver metastases.


METHODS
A total of 19 patients with liver metastases from colorectal cancer treated in 25 sessions were included in the present study. All patients had undergone fluorodeoxyglucose-PET for patient evaluation before interstitial CT-guided brachytherapy. A contrast-enhanced CT scan of the upper abdomen was obtained for radiation planning. The clinical target volume (CTV) was defined by a radiation oncologist and radiologist. After registration of the CT scan with the PET data set, the target volume was defined again using the fusion images.


RESULTS
PET revealed one additional liver lesion that was not visible on CT. The median CT-CTV (defined using CT and magnetic resonance imaging) was 68 cm(3) (range 4-260). The PET/CT-CTV (median, 78 cm(3); range, 4-273) was significantly larger, with a median gain of 24.5% (interquartile range, 2.1-71.5%; p = .022). An increased CTV was observed in 15 cases and a decrease in 6; in 4 cases, the CT-CTV and PET/CT-CTV were equal. Incomplete dose coverage of PET/CT-CTVs was indicative of early local progression (p = .004); however, CT-based radiation plans did not show significant differences in the local control rates when stratified by dose coverage.


CONCLUSIONS
Retrospective implementation of fluorodeoxyglucose-PET for CTV specification for CT-guided brachytherapy for colorectal liver metastases revealed a significant change in the CTVs. Additional PET-positive tumor regions with incomplete dose coverage could explain unexpected early local progression.
Steffen
Ingo G
IG
Klinik für Strahlenheilkunde, Campus Virchow-Klinikum, Charité-Universitätsmedizin Berlin, Berlin, Germany.
Wust
Peter
P
Rühl
Ricarda
R
Grieser
Christian
C
Schnapauff
Dirk
D
Lüdemann
Lutz
L
Grabik
Wojciech
W
Ricke
Jens
J
Amthauer
Holger
H
Hamm
Bernd
B
Hänninen
Enrique Lopez
EL
Denecke
Timm
T
D000368:Aged; D000369:Aged, 80 and over; D001918:Brachytherapy / Q000379:methods*; D015179:Colorectal Neoplasms; D018450:Disease Progression; D005260:Female; D019788:Fluorodeoxyglucose F18; D006801:Humans; D008113:Liver Neoplasms / Q000000981:diagnostic imaging / Q000532:radiotherapy / Q000556:secondary; D008297:Male; D008875:Middle Aged; D009367:Neoplasm Staging / Q000379:methods; D049268:Positron-Emission Tomography / Q000379:methods*; D019275:Radiopharmaceuticals; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods*; D012189:Retrospective Studies; D014057:Tomography, X-Ray Computed / Q000379:methods*; D047368:Tumor Burden
D019275:Radiopharmaceuticals; D019788:Fluorodeoxyglucose F18