Lack of Anatomical Concordance between Preablation and Postablation CT Images: A Risk Factor Related to Ablation Site Recurrence

Abstract

Objective. Variation in the position of the liver between preablation and postablation CT images hampers assessment of treatment of colorectal liver metastasis (CRLM). The aim of this study was to test the hypothesis that discordant preablation and postablation imaging is associated with more ablation site recurrences (ASRs). Methods. Patients with CRLM were included. Index-tumor size, location, number, RFA approachs and ablative margins were obtained on CT scans. Preablation and postablation CT images were assigned a “Similarity of Positioning Score” (SiPS). A suitable cutoff was determined. Images were classified as identical (SiPS-id) or nonidentical (SiPS-diff). ASR was identified prospectively on follow-up imaging. Results. Forty-seven patients with 97 tumors underwent 64 RFA procedures (39 patients/63 tumors open RFA, 25 patients/34 tumours CT-targeted RFA, 12 patients underwent >1 RFA). Images of 52 (54%) ablation sites were classified as SiPS-id, 45 (46%) as SiPS-diff. Index-tumor size, tumor location and number, concomitant partial hepatectomy, and RFA approach did not influence the SiPS. ASR developed in 11/47 (23%) patients and 20/97 (21%) tumours. ASR occurred less frequently after open RFA than after CT targeted RFA (P < 0.001). ASR was associated with larger index-tumour size (18.9 versus 12.8 mm, P = 0.011). Cox proportional hazard model confirmed SiPS-diff, index-tumour size >20 mm and CT-targeted RFA as independent risk factors for ASR. Conclusion. Variation in anatomical concordance between preablation and postablation images, index-tumor size, and a CT-targeted approach are risk factors for ASR in CRLM.

Radiofrequency ablation as an alternative to hepatic resection for single small hepatocellular carcinomas

“…Tumour recurrence was defined as the appearance of new lesion(s) with typical radiological features of HCC. Treatment‐site recurrence (recurrence at the ablation or resection site) was defined by the reappearance of viable tumour within or directly adjacent to the ablated or resected site, where the largest diameter was in direct contact with the treated site. Non‐treatment‐site recurrence included distant intrahepatic recurrence and extrahepatic recurrence.…”

Radiofrequency ablation versus transarterial chemoembolization for unresectable solitary hepatocellular carcinomas sized 5–8 cm

“…All patients with complete ablation after RFA were monitored for intrahepatic recurrence or distant metastasis according to serum alpha‐fetoprotein level, chest radiography and CT every 3 months. Ablation site recurrence was defined as the growth of a contrast‐enhancing lesion within or directly adjacent to the ablation zone if the largest diameter of the lesion was in direct contact with the ablation zone . Distant intrahepatic recurrence was defined as the occurrence of a new tumour in the liver in an area distinct from the ablated area.…”

Stereotactic image guided microwave ablation of HCC: A step forward and still a long way to go

“…It is of great importance that “ablationists” apply a uniform definition of ASR. We strongly advocate the definition in which the largest diameter of the recurrence is in contact with the outer ablation zone . Only then should recurrences be called ASRs.…”