Improved detection of local tumor progression after ablation or resection of colorectal liver metastases using [¹⁸F]FDG-PET/contrast-enhanced CT versus contrast-enhanced CT alone

Abstract

Objective: Post-treatment surveillance after locally treated colorectal liver metastases involves CEA measurement and contrast-enhanced CT (CECT) scans. However, reactive tissue around ablated lesions can appear similar to viable tumor tissue on CECT, complicating the detection of local tumor progression (LTP). Therefore, a new imaging protocol was initiated, which incorporates [¹⁸F]FDG-PET/CT to complement CECT. This study evaluated the diagnostic accuracy of [¹⁸F]FDG-PET/CECT for early detection of disease progression after resection or thermal ablation, compared to CECT alone. Materials and methods: The study analyzed a prospective cohort of patients undergoing thermal ablation or resection, who received CECT and [¹⁸F]FDG-PET/CT scans 3–5 months post-treatment. Disease progression was confirmed by histology, consensus during a multidisciplinary team meeting or after extended follow-up. Diagnostic accuracy of [¹⁸F]FDG-PET/CECT was compared to standard practice (CEA serum levels and CECT). Results: The final analysis included 64 patients with 154 lesions. 37 patients underwent ablation, 14 patients underwent resection, and 13 patients underwent combination therapy, resulting in 93 (60%) lesions being treated with thermal ablation and 61 (40%) lesions with resection. Disease progression was found in 66% of patients, with LTP detected in 25% of treated lesions. Compared to CECT, [¹⁸F]FDG-PET/CECT had a higher diagnostic accuracy for detecting local progression after thermal ablation (AUC 0.97 vs. 0.73, p = 0.001) and hepatic resection (AUC 0.96 vs. 0.69, p = 0.03), and for detection of extrahepatic disease (AUC 0.91 vs. 0.79, p = 0.03). CEA serum levels had low diagnostic accuracy for detecting disease progression (AUC 0.60). Conclusion: [¹⁸F]FDG-PET/CECT improves diagnostic accuracy in the early follow-up of patients with locally treated colorectal liver metastases. Key Points: Question : Interpreting CECT scans after local treatment of colorectal liver metastases can be challenging because reactive tissue around treated lesions can appear similar to viable tumor tissue. Findings : [¹⁸F]FDG-PET/CECT improves the diagnostic accuracy of detecting local tumor progression after thermal ablation and resection of colorectal liver metastases. Clinical relevance : [¹⁸F]FDG-PET/CECT should be considered during follow-up after local treatment of colorectal liver metastases to identify and treat local tumor progression earlier.