The Value of 18F-FDG-PET-CT Imaging in Treatment Evaluation of Colorectal Liver Metastases: A Systematic Review

Abstract

(1) Background: Up to 50% of patients with colorectal cancer either have synchronous colorectal liver metastases (CRLM) or develop CRLM over the course of their disease. Surgery and thermal ablation are the most common local treatment options of choice. Despite development and improvement in local treatment options, (local) recurrence remains a significant clinical problem. Many different imaging modalities can be used in the follow-up after treatment of CRLM, lacking evidence-based international consensus on the modality of choice. In this systematic review, we evaluated ¹⁸F-FDG-PET-CT performance after surgical resection, thermal ablation, radioembolization, and neoadjuvant and palliative chemotherapy based on current published literature. (2) Methods: A systematic literature search was performed on the PubMed database. (3) Results: A total of 31 original articles were included in the analysis. Only one suitable study was found describing the role of ¹⁸F-FDG-PET-CT after surgery, which makes it hard to draw a firm conclusion. ¹⁸F-FDG-PET-CT showed to be of additional value in the follow-up after thermal ablation, palliative chemotherapy, and radioembolization. ¹⁸F-FDG-PET-CT was found to be a poor to moderate predictor of pathologic response after neoadjuvant chemotherapy. (4) Conclusions: ¹⁸F-FDG-PET-CT is superior to conventional morphological imaging modalities in the early detection of residual disease after thermal ablation and in the treatment evaluation and prediction of prognosis during palliative chemotherapy and after radioembolization, and ¹⁸F-FDG-PET-CT could be considered in selected cases after neoadjuvant chemotherapy and surgical resection.

Keywords: colorectal cancer; colorectal liver metastases; follow-up; positron emission tomography.

Figure 1

PRISMA flow chart.

Figure 2

Follow-up ceCT image three months after RFA, suggesting clear ablation margins (black arrow) and no residual tumor (A). Simultaneous ¹⁸F-FDG-PET-CT image of the same patient showing high focal FDG uptake in the tumor periphery (white arrow) strongly suspected of residual disease (B). Three months later, CEA levels had risen, and the focal FDG uptake had spread, confirming tumor residue at the ablation site.

Figure 3

¹⁸F-FDG PET-CT images of a patient before and after receiving neoadjuvant chemotherapy. ¹⁸F-FDG PET-CT fusion image with high focal FDG uptake in segment 4A indicative of a colorectal liver metastasis, white arrow (A); ¹⁸F-FDG PET-CT fusion image after 3 cycles of neoadjuvant chemotherapy (FOLFOXIRI-bevacuzimab) showing solely physiological FDG uptake in healthy liver parenchyma (B) indicating a complete metabolic response.

Figure 4

¹⁸F-FDG PET-CT images before and 6 weeks after radioembolization. Coronal PET-only images (left panel), fused ¹⁸F-FDG PET-CT images (A,C), and contrast-enhanced CT images (B,D). Pretreatment ¹⁸F-FDG PET-CT and contrast-enhanced CT images show multiple hepatic lesions (A,B). Posttreatment ¹⁸F-FDG PET-CT imaging shows a partial metabolic response (C), whereas contrast-enhanced CT imaging suggests progressive disease. Adapted from: The role of early ¹⁸F-FDG PET/CT in prediction of progression-free survival after 90Y radioembolization: comparison with RECIST and tumour density criteria. I. Zerizer et al. Eur J Nucl Med Mol Imaging. 2012 Sep;39(9):1391-9. doi: 10.1007/s00259-012-2149-1. Epub 2012 May 30.