Colorectal cancer: the role of PET/CT in recurrence

Abstract

Many imaging modalities and scanning techniques, such as contrast enhanced CT, MRI and FDG-PET, are available for assessment of recurrent colorectal carcinoma. In addition, integrated PET/CT is becoming increasingly available. Intuitively, a synergistic combination of scanning characteristics sounds promising. However, the exact clinical value has not yet been fully established. The role of PET/CT image fusion must be weighed carefully against other available modalities. In this review we evaluate the potential of combined PET/CT in recurrent colorectal carcinoma. When available, PET/CT currently appears the diagnostic tool of choice. In the near future, combined PET/MRI may further enhance the diagnostic algorithm.

Figure 1

Image fusion of contrast-enhanced CT and FDG-PET. The images show axial and coronal slices of CT (a, c) and PET (b, d) through the abdomen. On the CT images, the pelvic recurrence is difficult to appreciate due to extensive tissue masses. Within these masses, the PET image clearly shows a pathological lesion consistent with local recurrence of malignancy behind the bladder (white arrow). Image fusion with CT provided sufficient anatomical reference to guide a surgical approach.

Figure 2

Image fusion of contrast-enhanced CT and FDG-PET. The images show transverse slices (a, b) and coronal slices (c, d) through the abdomen of a patient who previously underwent primary resection of a sigmoid carcinoma. The PET image clearly showed a pathological lesion (white arrow), but the cause remained unclear as no clear lymph node was found, and the dilated ureter suggested another explanation (black arrow). Image fusion with CT could demonstrate correlation with a lymph node that was overlooked before.

Figure 3

Image fusion of contrast-enhanced CT and FDG-PET. The images show transverse slices of the abdomen through the liver, from CT (a), PET (b) and PET/CT (c). PET shows a clear metastasis in the ventral border of the liver that is hardly visible on CT, indicating the high sensitivity of FDG-PET, but also illustrating the need for correlation with anatomical imaging. Furthermore, the image illustrates that FDG-PET is unaffected by the extensive residual changes and surgical clips posterior in the right liver lobe, after partial liver resection.

Figure 4

Software image fusion of CT, MRI and FDG-PET. The images show transverse slices through the liver of a patient who underwent prior RFA treatment (upper arrow) and liver resection for liver metastasis of colon carcinoma. Both CT (a) and MRI (c) are difficult to interpret in the region of the surgical clips. The PET image (b) clearly shows a recurrent liver metastasis (lower arrow), which could be localized only after image fusion with MRI (d). This permitted guided locoregional therapy.