TORONTO--Visualization of gastrointestinal carcinomas is enhanced
with the use of a radiolabeled peptide developed at the University of
Vienna, according to a study presented at the 45th Annual Meeting of
the Society of Nuclear Medicine (SNM).
Studies have shown that many GI tumors have receptors for vasoactive
intestinal peptide (VIP), said Shuren Li, MD, Department of Nuclear
Medicine, University of Vienna, and receptor scanning with
iodine-123-labeled VIP (123I-VIP) can identify hot spots
associated with colorectal cancer.
"There is no cure for advanced colorectal cancer," Dr. Li
said, "so early detection of disease influences the prognosis of
the patients. We offer receptor scintigraphy as a way to identify
small metastatic lesions and to differentiate lesions from operative scarring."
Eighty patients with confirmed colo-rectal adenocarcinoma underwent
receptor scintigraphy with 123I-VIP (1µg to 150 MBq).
Two independent physicians evaluated each scan, and patients were
followed for at least 6 months or until death with regular CT scans
every 8 weeks. However, Dr. Li pointed out, all comparisons between 123I-VIP
and CT were done with scans taken within 4 weeks of each other.
Of the 80 patients, 13 were free of tumor after previous resection; 8
presented with primary tumors; 14 had locally recurrent tumors but no
metastases; 10 had locally recurrent tumors with metastases to the
liver, lung, or lymph nodes; and 35 had disease confined to organ metastases.
Fourteen of the patients with advanced colorectal cancer also
presented with adenomatous polyps at the time of screening.
The 123I-VIP scans were negative in all 13 curatively
resected patients, Dr. Li reported. VIP receptor scans identified 7
(87%) of the 8 primary tumors and 21 (82%) of the 24 locally
recurrent tumors. All 4 patients with lymph node metastases had
positive scans; 25 (89%) of the 28 liver metastases were identified (Figure),
as were 2 (67%) of the 3 lung metastases.
In four patients with relapsing cancer, the 123I-VIP scans
indicated the presence of disease before CT imaging. Also, in two
patients with suspicious CT scans, the 123I-VIP scan
identified the areas as surgical scar tissue. There was no 123I-VIP
tracer uptake seen in the adeno-matous polyps.
Speaking at a press conference held in conjunction with the SNM
meeting, Markus Raderer, MD, lead author of the study, said that
"incorporation of VIP into the clinical workup of patients with
a history of colorectal cancer can provide additional information to
conventional radiologic methods, both in the staging of patients with
documented disease and in patients with suspected recurrence."
Dr. Raderer noted that the researchers are currently developing a
technetium-99m-labeled VIP, "which would clearly facilitate
widespread use of this compound." His group is also conducting a
study comparing 123I-VIP with fluorine-18
fluorodeoxyglucose (FDG) imaging with PET in patients with colorectal cancer.