TORONTOSeveral studies presented at the Society of Nuclear
Medicines 45th annual conference support the use of positron
emission tomography (PET) with fluorine-18-fluorodeoxyglucose (FDG)
to evaluate patients with recurrent colorectal cancer.
FDG-PET is more accurate than the conventional diagnostic
modalities for staging patients with recurrent colorectal carcinoma,
and has a significant positive impact on patient management in this
setting, said Patrick Flamen, MD, of the Department of Nuclear
Medicine, KU Leuven-UZ Gasthuisberg, Leuven, Belgium. The
advantage of whole-body FDG-PET is that screening is performed in one
examination and that unsuspected metastatic sites can be
detected, he added.
The Belgium researchers retrospectively reviewed 103 patients with
suspected recurrent colorectal cancer who underwent whole body
FDG-PET in addition to conventional staging (CEA, endoscopy, CT of
the chest and abdomen, MRI, and ultrasound). The PET studies were
interpreted with full knowledge of the conventional staging findings.
Of the 37 patients with pelvic recurrence, PET detected 30 cases
(81%) whereas CT detected only 22 (59%). Of the 48 patients with
liver metastases, PET detected 96%, which was slightly better than CT
The sensitivity to the detection of retroperitoneal lymph node
involvement was similar for both PET and conventional staging methods
(73%). Neither PET nor CT was able to accurately detect peritoneal
involvement. PET located all 14 extraab-dominal lesions whereas
conventional staging missed 4 such lesions.
As for patient management, conventional staging had categorized 64
patients as operable and 22 as having extended disease. The addition
of PET findings correctly downstaged 5 patients and upstaged 11
patients. However, 2 patients were incorrectly overstaged and 5 were
under-staged with PET scanning.
In 9 patients with elevated serum CEA who had negative or equivocal
conventional staging results, PET correctly detected relapse in 5
patients and excluded disease in 2 patients.
Researchers from the University of Frankfurt, Main, Germany, Medical
Center emphasized the role of FDG-PET in detecting extrahepatic
metastases before liver surgery in patients with recurrent colorectal cancer.
The goal of the study was to determine a way to select patients
for curative hepatic resection and avoid surgery in patients with
extrahepatic lesions, said Dr. Andreas Hertel, of the
Department of Nuclear Medicine at University Hospital, Frankfurt.
We believe that FDG-PET may be a cost-effective way to screen
patients with recurrent colorectal cancer, Dr. Hertel added.
The Frankfurt study included 36 colorectal cancer patients with
suspected or known liver lesions. Prior to surgery, all underwent CT
and FDG-PET imaging. The sensitivity of PET was superior to CT for
the identification of metastatic lesions and led to changes in
management in 39% of patients, Dr. Hertel said. PET imaging allowed
surgeons to perform curative surgery in 4 patients with local
recurrence only and avoid surgery in 10 patients with previously
undetected multiple extrahepatic metastases.
Lead author Richard P. Baum, MD, chair of the Bad Berka PET Center,
said: Our prospective data clearly indicate that whole body
FDG-PET is the most accurate noninvasive method for restaging
colorec-tal cancer patients before liver surgery. FDG-PET had a
decisive influence on the therapeutic strategy in more than one-third
of our patients.
Dr. Baum recommends FDG-PET for certain clearly defined situations in
the evaluation of colorectal cancer:
Patients to be treated with regional chemotherapy of the liver.
Patients with normal CT, MRI, and/or ultrasound tests and elevated
Patients diagnosed with a primary tumor when thoracic x-ray and
abdominal ultrasound are normal but CEA levels are elevated.
Dr. Baum cited an example in which FDG-PET changed one patients
planned surgery. The patient was scheduled for surgery to remove a
single liver mass located with conventional imaging methods. However,
FDG-PET imaging located an unknown lung metastasis. The surgeon then
removed both masses, and the patient remains tumor free at 18 months post-surgery.
Dr. Baum also described a patient who had a single lung metastasis.
But because the presurgical PET scan also detected mediastinal
metastasis (an indication for chemotherapy, not surgery), the
operation was canceled.