The Role and Limitations of 18-Fluoro-2-deoxy-d-glucose Positron Emission Tomography (FDG-PET) Scan and Computerized Tomography (CT) in Restaging Patients with Hepatic Colorectal Metastases Following Neoadjuvant Chemotherapy: Comparison with Operative and Pathological Findings

Abstract

BackgroundRecent data confirmed the importance of 18-fluoro-2-deoxy-d-glucose positron emission tomography (FDG-PET) in the selection of patients with colorectal hepatic metastases for surgery. Neoadjuvant chemotherapy before hepatic resection in selected cases may improve outcome. The influence of chemotherapy on the sensitivity of FDG-PET and CT in detecting liver metastases is not known.MethodsPatients were assigned to either neoadjuvant treatment or immediate hepatic resection according to resectability, risk of recurrence, extrahepatic disease, and patient preference. Two-thirds of them underwent FDG-PET/CT before chemotherapy; all underwent preoperative contrast-enhanced CT and FDG-PET/CT. Those without extensive extrahepatic disease underwent open exploration and resection of all the metastases according to original imaging findings. Operative and pathological findings were compared to imaging results.ResultsTwenty-seven patients (33 lesions) underwent immediate hepatic resection (group 1), and 48 patients (122 lesions) received preoperative neoadjuvant chemotherapy (group 2). Sensitivity of FDG-PET and CT in detecting colorectal (CR) metastases was significantly higher in group 1 than in group 2 (FDG-PET: 93.3 vs 49%, P < 0.0001; CT: 87.5 vs 65.3, P = 0.038). CT had a higher sensitivity than FDG-PET in detecting CR metastases following neoadjuvant therapy (65.3 vs 49%, P < 0.0001). Sensitivity of FDG-PET, but not of CT, was lower in group 2 patients whose chemotherapy included bevacizumab compared to patients who did not receive bevacizumab (39 vs 59%, P = 0.068).ConclusionsFDG-PET/CT sensitivity is lowered by neoadjuvant chemotherapy. CT is more sensitive than FDG-PET in detecting CR metastases following neoadjuvant therapy. Surgical decision-making requires information from multiple imaging modalities and pretreatment findings. Baseline FDG-PET and CT before neoadjuvant therapy are mandatory.

Response to chemotherapy predicts survival following resection of hepatic colo‐rectal metastases in patients treated with neoadjuvant therapy

“…The utility of this preoperative study was also shown by Strasberg et al [30] to lessen tumor recurrence in a chemo-naïve patient cohort undergoing hepatic resection for colorectal metastases. However, it is now known that the sensitivity of FDG-PET is reduced following neoadjuvant chemotherapy, especially in patients who received bevacizumab, as was demonstrated in a previous series at our institution [31]. Nevertheless, the combined results of PET and high resolution CT may increase the accuracy of preoperative staging before hepatic resection [32] and is regularly used at our institution for evaluation of colorectal liver metastases.…”

Staging of colorectal liver metastases after preoperative chemotherapy. Diffusion-weighted imaging in combination with Gd-EOB-DTPA MRI sequences increases sensitivity and diagnostic accuracy

“…Difficulties in restaging the liver disease after chemotherapy derive from various aspects. Firstly, treated lesions often exhibit reduced contrast in respect to the liver parenchyma and illdefined borders [9] as a consequence of a decrease in tumour size to sub-centimetre diameters or of a druginduced steatosis [10], which modifies the imaging aspect of the liver parenchyma. Secondly, patients often commence chemotherapy without high-quality pretreatment imaging used for comparison.…”

“…However, staging the liver disease after chemotherapy is more difficult, and the sensitivity of preoperative imaging in such patients is significantly inferior to that observed in chemotherapy-naïve patients (CT: 65.3 % versus 87.5 %; PET 49 % versus 93.3 %, respectively) [9]. This has been attributed to the aspect of post-chemotherapy metastases that often have reduced contrast in respect to the liver and ill-defined borders [9]. Although these morphological characteristics might simply be the consequence of a decrease in tumour size to sub-centimetre diameters, frequently they are determined by a drug-induced steatosis [10], which modifies the imaging aspect of the liver parenchyma.…”

“…Therefore, accurate detection and localisation of all metastatic deposits is essential to determine the resectability, which is now defined solely according to the possibility to obtain a radical (R0) resection [8]. However, staging the liver disease after chemotherapy is more difficult, and the sensitivity of preoperative imaging in such patients is significantly inferior to that observed in chemotherapy-naïve patients (CT: 65.3 % versus 87.5 %; PET 49 % versus 93.3 %, respectively) [9]. This has been attributed to the aspect of post-chemotherapy metastases that often have reduced contrast in respect to the liver and ill-defined borders [9].…”

Preoperative Imaging in Colorectal Liver Metastases: Current Practices

“…Neoadjuvant regimens including irinotecan and oxliplatin have the most biologic activity but also result in hepatotoxicity [38][39][40]. Neoadjuvant therapy results in decreased sensitivity of preoperative imaging for identification of existing colorectal hepatic metastasis [41,42]. As the use of neoadjuvant therapy expands, preoperative decisions regarding eligible surgical candidates will become more challenging.…”