18F-labeled fluorodeoxyglucose positron emission tomography-guided surgery for recurrent colorectal cancer: a...

Positron emission tomography (PET) scanning is an accepted diagnostic tool for the detection of colorectal cancer (CRC). The purpose of this study was to determine whether diagnostic information offered by preoperative PET scan could be used to detect disease intraoperatively using beta and gamma handheld probes.

Two studies were carried out. First, tumor "phantoms" were created using 62 microCi fluorodeoxyglucose (FDG) in a saline-filled basin. Gamma and beta handheld probes were used to determine detection characteristics with respect to probe type, distance from source, and isotope half-life. In a second study, probes were used intraoperatively to detect tumor in 10 patients with recurrent colorectal cancer as determined by preoperative PET scan. Counts relative to background were determined for each probe as was histopathologic correlation with probe-positive tissue.

Phantom studies documented that FDG detection by each probe was nonlinearly related to source proximity and half-life. In human subjects, abnormal findings on preoperative PET studies were detected by both probes with tumor:normal ratios of 1.6 (beta) and 1.5 (gamma). All probe-positive tissue was histologically confirmed to be recurrent colorectal cancer.

Intraoperative detection of CRC using an FDG source and beta and gamma probes correlates with preoperative PET. With further improvements in probe technology, successful differentiation of normal and tumor tissue as shown here may allow for more precise localization and directed resection.