FDG-PET/CT imaging for staging and target volume delineation in preoperative conformal radiotherapy of rectal cancer.
OBJECTIVE
To investigate the potential impact of using (18)F-fluorodeoxyglucose positron emission tomography/computed tomography (FDG-PET/CT) on staging and target volume delineation for patients affected by rectal cancer and candidates for preoperative conformal radiotherapy.


METHODS
Twenty-five patients diagnosed with rectal cancer T3-4 N0-1 M0-1 and candidates for preoperative radiotherapy underwent PET/CT simulation after injection of 5.18 MBq/kg of FDG. Clinical stage was reassessed on the basis of FDG-PET/CT findings. The gross tumor volume (GTV) and the clinical target volume (CTV) were delineated first on CT and then on PET/CT images. The PET/CT-GTV and PET/CT-CTV were analyzed and compared with CT-GTV and CT-CTV, respectively.


RESULTS
In 4 of 25 cases (24%), PET/CT affected tumor staging or the treatment purpose. In 3 of 25 cases (12%) staged N0 M0, PET/CT showed FDG uptake in regional lymph nodes and in a case also in the liver. In a patient with a single liver metastasis PET/CT detected multiple lesions, changing the treatment intent from curative to palliative. The PET/CT-GTV and PET/CT-CTV were significantly greater than the CT-GTV (p = 0.00013) and CT-CTV (p = 0.00002), respectively. The mean difference between PET/CT-GTV and CT-GTV was 25.4% and between PET/CT-CTV and CT-CTV was 4.1%.


CONCLUSIONS
Imaging with PET/CT for preoperative radiotherapy of rectal cancer may lead to a change in staging and target volume delineation. Stage variation was observed in 12% of cases and a change of treatment intent in 4%. The GTV and CTV changed significantly, with a mean increase in size of 25% and 4%, respectively.
Bassi
Maria Chiara
MC
Department of Radiotherapy, University of Piemonte Orientale, Novara, Italy.
Turri
Lucia
L
Sacchetti
Gianmauro
G
Loi
Gianfranco
G
Cannillo
Barbara
B
La Mattina
Pierdaniele
P
Brambilla
Marco
M
Inglese
Eugenio
E
Krengli
Marco
M
D000328:Adult; D000368:Aged; D001822:Body Burden; D005260:Female; D019788:Fluorodeoxyglucose F18; D006801:Humans; D008113:Liver Neoplasms / Q000556:secondary; D008207:Lymphatic Metastasis / Q000000981:diagnostic imaging; D008297:Male; D008875:Middle Aged; D009367:Neoplasm Staging / Q000379:methods; D049268:Positron-Emission Tomography / Q000379:methods*; D019275:Radiopharmaceuticals; D020266:Radiotherapy, Conformal; D012004:Rectal Neoplasms / Q000000981:diagnostic imaging / Q000473:pathology; D014057:Tomography, X-Ray Computed / Q000379:methods*
D019275:Radiopharmaceuticals; D019788:Fluorodeoxyglucose F18