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

Abstract

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.