ABSTRACT

A 73-year-old woman with known diagnosis of chronic hepatitis B infection referred for ¹⁸F-fluorodeoxyglucose positron emission tomography/ computed tomography (¹⁸F-FDG PET/CT) and magnetic resonance imaging (MRI) after detection of a liver mass with 9 cm diameter in contrast enhanced CT. However, ¹⁸F-FDG PET/CT and MRI revealed diffuse infiltrating hepatocellular carcinoma lesions other than previously defined mass. After 9 months of Sorafenib treatment serum alpha feto protein levels dropped from 60,500 ng/mL to 801 ng/mL. Later ¹⁸F-FDG PET/MRI was performed for evaluation of response to treatment and revealed marked response to treatment.

HCC is one of the most prevalent cancers in the world (1,2). In advanced HCC cases treatment choices can be limited to systemic treatments such as tyrosine-kinase receptor inhibitors, vascular endothelial growth factor inhibitors and immunotherapy agents (3,4,5). As one of the most commonly used tyrosine-kinase inhibitors, sorafenib can increase overall survival in HCC patients (6). It has been shown that pretreatment ¹⁸F-FDG PET/CT parameters have a prognostic value in HCC patients treated with sorafenib but intensity of ¹⁸F-FDG uptake may not predict response to sorafenib treatment (7,8). In this case the lesions previously undetected in CT were demonstrated with both components of PET/MRI. Additionally, ¹⁸F-FDG PET revealed different characteristics of these two pathologies, one being solitary non-FDG avid mass, other being intensely FDG-avid infiltrating lesions. Furthermore, more ¹⁸F-FDG avid infiltrating lesions had a marked response to sorafenib while the other large solid mass was merely exhibiting stable disease. An effective response to sorafenib is rare, and in this case both PET and MRI revealed dramatic response of infiltrating lesions to treatment, consistent with clinical findings. In conclusion, PET can reveal metabolic characteristics of HCC lesions and usage of high soft tissue contrast of MRI can help identify corresponding lesions in liver. This could make the usage of PET/MRI valuable for diagnosis, staging and as demonstrated above evaluation of response to treatment.