Clinical assessment of positron emission tomography for the diagnosis of local recurrence in colorectal cancer

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Abstract
Background: The clinical value of positron emission tomography (PET) for the diagnosis of local pelvic recurrence of colorectal cancer was evaluated. Methods: Computed tomography (CT) and magnetic resonance imaging (MRI) of the pelvis were performed at regular intervals in 23 patients who had undergone resection for colorectal cancer. The 23 patients had a total of 25 lesions. PET images of the 25 lesions and of six primary lesions in patients with rectal cancer were obtained. A differential absorption ratio (DAR) was calculated in order to examine the accumulation of [18F]2-fluoro-2-deoxy-d-glucose (18FDG) on PET images. Histological diagnoses of the pelvic masses were obtained by CT-guided needle biopsy. Results: On CT or MRI, a pelvic mass with a spicular shape (n = 1) was non-recurrent, whereas a nodular or lumpy shape indicated a locally recurrent lesion (n = 10). Masses with a nodulospicular shape (n = 12) did not correlate with the histological features. On PET, 15 of 16 histologically proven local recurrences were imaged positively. By setting a DAR of 2·8 as a cut-off value, local recurrences could be diagnosed with 100 per cent accuracy. Conclusion: PET is a clinically useful tool for the detection of local recurrence of colorectal cancer, particularly for distinguishing between recurrence and granulation tissues in the pelvic cavity.

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