Whole-body fluorine 18 fluorodeoxyglucose PET in combination with CT offers high sensitivity and specificity in detecting the recurrence or metastasis of colorectal cancer.

Whole-body fluorine 18 fluorodeoxyglucose PET in combination with CT offers high sensitivity and specificity in detecting the recurrence or metastasis of colorectal cancer, according to a retrospective study carried out at Jinling Hospital, School of Medicine, Nanjing University, China.

The findings are reported in the October 7 issue of the World Journal of Gastroenterology by Dr. Long-Bang Chen and colleagues.

The 68 patients (48 male, 20 female) were examined by PET/CT, an average of 2.5 years after surgery for colorectal cancer.

Recurrence or metastasis was confirmed in 56 patients during clinical follow-up five to 28 months after imaging.

The sensitivity of PET/CT diagnosis of CRC recurrence or metastasis was 94.6 per cent, and the specificity was 83.3 per cent. The positive predictive value was 96.4 per cent, and the negative predictive value was 76.9 per cent.

The major causes of false positives were granulomatous inflammation at the anastomosis and inflamed lymph node, while the major cause of false negatives was small lesion size, typically less than 1 cm in diameter.

In 8 cases in which abdominal/pelvic CT or ultrasound had shown negative findings, the PET/CT imaging detected one or more occult malignant lesions, resulting in an altered clinical approach. In 17 of the 56 cases (30.4 per cent), PET/CT detected more lesions than did CT and ultrasound, showing disseminated metastases.

The researchers comment that combined PET/CT imaging is especially important for identifying lesions in the abdominal and pelvic cavity, where PET alone "is insufficient to identify anatomic structures clearly."

They also noted that of the ten cases in which follow-up surgery had been planned prior to the PET/CT imaging, unnecessary surgeries were avoided in seven cases, because multiple distant metastases were found by PET/CT imaging.

World J Gastroenterol 2007;13:5025-5029.

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