TORONTO--New research suggests that tumor marker levels for
colorectal cancer do not consistently indicate the presence of
malignant tissue. A German study revealed that 10 of 34 patients with
colorectal cancer had normal carcinoembryonic antigen (CEA) levels
and 16 had normal CA19-9 levels. In addition, a California study
found that patients with elevated CEA levels did not necessarily have
"Tumor markers are an inexpensive follow-up procedure for
identifying the recurrence of colorectal cancer," said Hans
Biersack, MD, PhD, president of the World Federation of Nuclear
Medicine and Biology and professor of nuclear medicine, University of
Bonn, Germany. "In general," he said, "an increase in
tumor marker levels suggests increased cancer activity. However, we
found that 59% and 70% of the patients with normal levels of CEA and
CA19-9, respectively, had tumors present."
The German protocol included 45 patients with either confirmed
colorectal cancer and a suspicion of recurrence or a suspected
primary tumor. Each patient was assessed for CEA and CA19-9 levels
and also received a whole-body 18F-fluorodeoxyglucose positron
emission tomography (FDG-PET) scan. Path-ologic findings were
confirmed by CT scan, MRI, ultrasound, surgery, or clinical follow-up.
Overall, 34 of 45 patients had confirmed colorectal cancer and 11 had
no malignancy. CEA identified 31 patients correctly--24 positive and
7 negative; CA19-9 was correct in 26 patients--19 positive and 7
negative. FDG-PET was 100% accurate in the detection of tumor. It
identified all 34 patients with disease and 8 with no disease. There
were three false-positive findings with PET.
In addition, when CEA and CA19-9 levels were elevated, FDG-PET
correctly identified 93% and 95% of the lesions, respectively. In
patients with normal CEA and CA19-9 levels, FDG-PET correctly
identified 94% and 96% of the lesions, respectively.
Speaking at a press conference, lead author Dr. Hans Bender,
professor of nuclear medicine, University of Bonn, said: "Our
data indicate that normal tumor marker levels do not exclude the
presence of malignant tissue. If there are indications of tumor
recurrence, such as lesions detected by CT or ultrasound or patient
discomfort, I would recommend whole body FDG-PET independent of CEA
or CA19-9 levels."
A study by the Northern California PET Imaging Center, Sacramento,
included 44 patients with elevated CEA levels, 30 of whom had
subsequently confirmed malignancies. Of these 44 patients, 27 had
negative CT scans, 17 had not had CT examination. All patients
underwent whole body FDG-PET.
"We found that FDG-PET was highly sensitive for disease
recurrence, finding the disease in 28 of 30 patients with tumors. It
was much more accurate than using the CEA levels as an indication of
disease," said Peter Valk, MD, medical director of the Center.
PET gave true-positive results in 70% of patients who had negative CT
findings," said Elma Abella-Columna, MD, a clinical fellow at
the Center. "Where available, PET should be part of the
diagnostic workup in these patients if there is suspicion of disease
recurrence," she said. Recurrence may be suspected in the
presence of rising CEA levels, pain, or a mass felt on physical exam.
"When PET is positive and surgery is intended," she said,
"CT may still be used for preoperative anatomic evaluation.
However, for diagnosis of recurrence, PET does a much better