Radiological Assessment and Follow-Up After Radiofrequency Ablation

Abstract

Close and regular follow-up is recommended for patients following radiofrequency ablation (RFA) [1]. Baseline ultrasound (US) examinations should be performed within 24 h after ablation to exclude complications. Contrast-enhanced imaging can be performed within 24 h for early evaluation of therapeutic responses or possible complications (e.g., residual tumor tissue) [2]. During follow-up, the effectiveness of RFA should also be assessed by imaging 1 month after treatment to assess the inflammation surrounding the ablation zone. Appropriate imaging modalities could be contrast-enhanced US (ceUS), contrast-enhanced computed tomography (ceCT), or contrast-enhanced magnetic resonance imaging (ceMRI). Liver function and serum α-fetoprotein (AFP) should also be measured in the first month after ablation. The combination of laboratory tests and imaging examinations can make definite assessments. Contrast-enhanced imaging should determine whether the tumor was entirely covered by the ablation zone, whether new HCC lesions have occurred, and whether any normal adjacent structures were affected during ablation. Tumors without enhancement in the ablation zone are considered completely ablated, and if any enhancement is observed, tumors should be considered incompletely ablated. A recurrent hepatic tumor can be classified as local tumor progress (LTP) or a distal intrahepatic recurrence. LTP is defined as a recurrent tumor that occurs inside or adjacent to the primary tumor volume following a complete ablation. Distal intrahepatic recurrences are defined as intrahepatic lesions that are separated from the ablation zone by more than 1 cm. Distant recurrences can include intrahepatic recurrences and extrahepatic metastases. RFA effectiveness should be assessed according to whether the technique was successfully implemented. Technical success is defined when the tumor was treated according to protocol and was completely covered by the ablation zone. Otherwise, the treatment is defined as a technical failure. Technique effectiveness refers to complete ablation of a macroscopic tumor at a prospectively defined time point (frequently 1 month post-treatment). For cases of complete ablation and no recurrence at 1 month post-treatment, follow-ups should include abdominal US, serum AFP, and liver function measurements. They should be performed every month for 3 months, then every 3 months until 2 years post-treatment. After 2 years post-treatment, follow-ups should be performed every 6 months. Contrast-enhanced imaging should be performed to confirm the diagnosis of suspicious lesions that are detected upon abdominal US or if serum AFP levels become elevated again. ceCT or ceMRI should be repeated every 6–12 months during follow-up [3].