Fluorodeoxyglucose whole-body positron emission tomography in colorectal cancer patients studied in routine daily practice.

Abstract

To evaluate the routine clinical value of attenuation-corrected whole-body fluorodeoxyglucose positron emission tomography in colorectal cancer, a total of 59 patients who were referred for evaluation of suspected or proven colorectal cancers were studied. Positron emission tomography scans were recorded using a Siemens ECAT Exact 921/47. Median follow-up after the positron emission tomography study was 11 (mean, 12.3; range, 1-21) months. According to computed tomography, coloscopy, and ultrasound, we recorded eight apparently false-positive results. During later follow-up, however, three of those cases, which were negative with computed tomography, magnetic resonance imaging, sonography, or laparoscopy, turned out to be true-positive instead. In 3 patients, a primary colorectal cancer was suspected; in 26 patients, a recurrence of colorectal cancer was suspected. Eight patients were studied for follow-up after the history of colorectal cancer with no suspicion of recurrence. In 12 patients, the rise of serum tumor marker concentrations was the reason for the positron emission tomography study; 12 patients with known metastatic disease were also included ("restaging"). With regard to the entire patient population, we found an overall sensitivity of 100 percent, a specificity of 67 percent, and positive and negative predictive values of 92 and 100 percent, respectively. Being merely confirmative with respect to tumor recurrence or distant metastases in the majority of patients, positron emission tomography revealed a primary tumor in one patient and confirmed metastatic foci in several patients that had not been delineated by other imaging modalities. A whole-body positron emission tomography scan provides optimum conditions to locate metastatic lesions that might not be seen otherwise. There is a trend showing that positron emission tomography diagnostics as a consequence of early increased tumor markers is a highly sensitive combination, because computed tomography and magnetic resonance imaging were not as sensitive in early recurrences. Positron emission tomography, as performed in daily clinical practice, proved to be a powerful diagnostic tool in our subset of colorectal cancer patients.