Positron emission tomography using 18-fluoro-2-deoxy-glucose (FDG-PET) can identify colorectal cancer recurrence in patients with suspicious clinical or radiological findings but normal carcinoembryonic antigen (CEA) levels. Positron emission tomography using 18-fluoro-2-deoxy-glucose (FDG-PET) can identify colorectal cancer recurrence in patients with suspicious clinical or radiological findings but normal carcinoembryonic antigen (CEA) levels, according to a report in the June 7th issue of the World Journal of Surgical Oncology.

"There will be a certain percentage of recurrent colorectal cancer patients that will have a normal CEA level (even when their CEA level was originally elevated at the time of their previous original colorectal cancer diagnosis)," Dr. Ismet Sarikaya from The Ohio State University, Columbus, told Reuters Health. "Therefore, one cannot rely solely upon CEA monitoring in colorectal cancer patients."

Dr. Sarikaya and associates analyzed the value of FDG-PET scans in 39 patients with normal CEA levels but clinical or radiological findings suspicious for tumor recurrence.

Twenty-six PET scans (67 per cent) were positive, the authors report, including 22 true positives (based on histopathological evidence of tumor recurrence) and four false positives.

Eight patients had true negative PET scans, and five patients had false negative PET scans.

Based on these values, the overall accuracy of PET was 76.9 per cent, with a sensitivity of 81.4 per cent, specificity of 66.6 per cent, positive predictive value of 84.6 per cent, and negative predictive value of 61.5 per cent.

"PET should be considered early in the evaluation of patients with suspected tumor recurrence," the authors conclude.

Dr. Sarikaya said his group recommends a FDG-PET scan in colorectal cancer patients with a normal CEA who have "clinically suspicious findings such as sign/symptoms of developing/evolving bowel obstruction, palpable masses, unexplained failure to thrive/weight loss, or unexplained lower GI blood loss." They extend their recommendation to patients who have radiographically suspicious findings, and those with suspicious findings on endoscopy, "irrespective of whether any endoscopic biopsies are positive or negative."

"We are planning to investigate combined perioperative and intraoperative methods of FDG detection and refinement of methods of cancer cell-targeted detection in both CRC patients with normal and abnormal CEA levels, as well as in other malignancies," Dr. Sarikaya commented.

"As this technology evolves, we expect to get better and better at evaluating the sites of recurrence and the extent of recurrence and applying this knowledge into the operating room for accomplishing a more complete resection of such disease," Dr. Sarikaya added.


Source: Reuters