Impact of the 18F-FDG-PET/MRI on Metastatic Staging in Patients with Hepatocellular Carcinoma: Initial Results from 104 Patients

Abstract

Optimal HCC therapeutic management relies on accurate tumor staging. Our aim was to assess the impact of 18F-FDG-WB-PET/MRI on HCC metastatic staging, compared with the standard of care CT-CAP/liver MRI combination, in patients with HCC referred on a curative intent or before transarterial radioembolization. One hundred and four consecutive patients followed for HCC were retrospectively included. The WB-PET/MRI was compared with the standard of care CT-CAP/liver MRI combination for HCC metastatic staging, with pathology, followup, and multidisciplinary board assessment as a reference standard. Thirty metastases were identified within 14 metastatic sites in 11 patients. The sensitivity of WB-PET/MRI for metastatic sites and metastatic patients was significantly higher than that of the CT-CAP/liver MRI combination (respectively 100% vs. 43%, p = 0.002; and 100% vs. 45%, p = 0.01). Metastatic sites missed by CT-CAP were bone (n = 5) and distant lymph node (n = 3) in BCLC C patients. For the remaining 93 nonmetastatic patients, three BCLC A patients identified as potentially metastatic on the CT-CAP/liver MRI combination were correctly ruled out with the WB-PET/MRI without significant increase in specificity (100% vs. 97%; p = 0.25). The WB-PET/MRI may improve HCC metastatic staging and could be performed as a "one-stop-shop" examination for HCC staging with a significant impact on therapeutic management in about 10% of patients especially in locally advanced HCC.

Keywords: 18F-Fluoro-Desoxy-Glucose; PET/MRI; hepatocellular carcinoma; metastases; staging.

Conflict of interest statement

Two authors (Aurélien Monnet and Alto Stemmer) are employees of Siemens Healthineers. Both authors enabled the optimization of whole-body MR protocols on our PET/MR system for this study. All other authors retained full control of all data and were responsible for all analyses performed in the study. The study did not receive any financial support from industry.

Figures

Figure 1

Flow Chart.

Figure 2

A 56-year-old patient referred to WB-PET/MRI before TARE. The CT-CAP (a) showed a solitary rounded 7 mm-size lung nodule (arrows). The WB-PET/MRI confirmed an infracentimetric lung nodule visible on morphologic sequences (T1-weighted after gadolinium injection) (b) with hyperintensity on b800 s/mm2 DWI (c) and 18F-FDG hypermetabolism (d) leading to the diagnosis of lung metastasis. The followup CT scan (e,f) performed three months after the WB-PET/MRI showed a significant progression of the number and size of lung nodules, confirming the metastatic status.

Figure 3

A 65-year-old BCLC C patient referred for a WB-PET/MRI before liver transplantation. On CT-CAP, no bone lesion was visible (a). The WB-PET/MRI revealed an infracentimetric bone lesion with enhancement after Gadolinium–chelate injection (b), together with hyperintensity on DWI (c), and focal hypermetabolism on 18F-FDG-PET (d) leading to the diagnosis of bone metastasis. Moreover, on CT-CAP, a retroperitoneal nonspecific lymph node was observed (e), visible on morphologic MRI sequence (f). Both diffusion restriction (g) and 18F-FDG hypermetabolism (h) were observed leading to the diagnosis of lymph node involvement. The patient was excluded from the liver transplantation list, with a rapidly progressing disease leading to patient death within three months.

Figure 4

A 68-year-old BCLC C patient referred to WB-PET/MRI before TARE. The CT-CAP performed (a) showed a 12 × 25 mm large mediastinal lymph node of indeterminate nature. The WB-PET/MRI revealed hyperintensity on b800 s/mm2 DWI (b) with hypermetabolism on 18F-FDG-PET (c) suggestive of metastatic involvement. Followup performed two months later confirmed the metastatic nature of the lymph nodes with rapid increase in size and necrosis (d).

Figure 5

A 61-year-old BCLC A patient referred for a WB-PET/MRI before liver surgery for HCC. On the liver MRI, a 2 cm large left adrenal nodule was observed without signal drop on out phase images (a,b). On the CT-CAP, the unenhanced adrenal mass density was 39UH, which was not able to confirm its benign nature (c). No hypermetabolism was observed on 18F-FDG-PET (d), leading to the exclusion of its metastatic nature. Surgery was performed and the adrenal lesion remained stable on the followup CT (e) and MRI (f) performed three and nine months after the WB-PET/MRI, respectively.

Figure 6

An 82-year-old BCLC A patient referred for a WB-PET/MRI before liver surgery for HCC. The CT-CAP showed an 11 mm large round-shaped pulmonary nodule (a). The nodule was also visible on the morphologic MRI sequence (b). There was no diffusion restriction (c) and no 18F-FDG hypermetabolism (d) leading to the exclusion of lung metastasis. Surgery was performed and, on CT followup performed two years after the WB-PET/MRI (e), the nodule remained stable without the appearance of additional lesions.