Margin Size is an Independent Predictor of Local Tumor Progression After Ablation of Colon Cancer Liver Metastases
Section of Interventional Radiology, Department of Radiology, Memorial Sloan-Kettering Cancer Center, 1275 York Ave., Room H118, New York, NY, 10065, USA. CardioVascular and Interventional Radiology
(Impact Factor: 2.07).
04/2012; 36(1). DOI: 10.1007/s00270-012-0377-1
This study was designed to evaluate the relationship between the minimal margin size and local tumor progression (LTP) following CT-guided radiofrequency ablation (RFA) of colorectal cancer liver metastases (CLM).
An institutional review board-approved, HIPPA-compliant review identified 73 patients with 94 previously untreated CLM that underwent RFA between March 2003 and May 2010, resulting in an ablation zone completely covering the tumor 4–8 weeks after RFA dynamic CT. Comparing the pre- with the post-RFA CT, the minimal margin size was categorized to 0, 1–5, 6–10, and 11–15 mm. Follow-up included CT every 2–4 months. Kaplan–Meier methodology and Cox regression analysis were used to evaluate the effect of the minimal margin size, tumor location, size, and proximity to a vessel on LTP.
Forty-five of 94 (47.9 %) CLM progressed locally. Median LTP-free survival (LPFS) was 16 months. Two-year LPFS rates for ablated CLM with minimal margin of 0, 1–5 mm, 6–10 mm, 11–15 mm were 26, 46, 74, and 80 % (p < 0.011). Minimal margin (p = 0.002) and tumor size (p = 0.028) were independent risk factors for LTP. The risk for LTP decreased by 46 % for each 5-mm increase in minimal margin size, whereas each additional 5-mm increase in tumor size increased the risk of LTP by 22 %.
An ablation zone with a minimal margin uniformly larger than 5 mm 4–8 weeks postablation CT is associated with the best local tumor control.
Available from: Sascha Zelzer
- "As with thermal ablation, the treatment zone after IRE must cover the entire tumor in addition to a safety margin. As demonstrated by Wang et al., the size of the safety margin plays a key role for the oncological success of focal tumor ablation . After radiofrequency ablation of colorectal liver metastases, they found that a safety margin uniformly larger than 5 mm, defined with post-interventional contrast-enhanced CT, is associated with better local tumor control. "
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ABSTRACT: Size and shape of the treatment zone after Irreversible electroporation (IRE) can be difficult to depict due to the use of multiple applicators with complex spatial configuration. Exact geometrical definition of the treatment zone, however, is mandatory for acute treatment control since incomplete tumor coverage results in limited oncological outcome. In this study, the "Chebyshev Center Concept" was introduced for CT 3d rendering to assess size and position of the maximum treatable tumor at a specific safety margin.
In seven pig livers, three different IRE protocols were applied to create treatment zones of different size and shape: Protocol 1 (n = 5 IREs), Protocol 2 (n = 5 IREs), and Protocol 3 (n = 5 IREs). Contrast-enhanced CT was used to assess the treatment zones. Technique A consisted of a semi-automated software prototype for CT 3d rendering with the "Chebyshev Center Concept" implemented (the "Chebyshev Center" is the center of the largest inscribed sphere within the treatment zone) with automated definition of parameters for size, shape and position. Technique B consisted of standard CT 3d analysis with manual definition of the same parameters but position.
For Protocol 1 and 2, short diameter of the treatment zone and diameter of the largest inscribed sphere within the treatment zone were not significantly different between Technique A and B. For Protocol 3, short diameter of the treatment zone and diameter of the largest inscribed sphere within the treatment zone were significantly smaller for Technique A compared with Technique B (41.1 +/- 13.1mm versus 53.8 +/- 1.1mm and 39.0 +/- 8.4mm versus 53.8 +/- 1.1mm; p < 0.05 and p < 0.01). For Protocol 1, 2 and 3, sphericity of the treatment zone was significantly larger for Technique A compared with B.
Regarding size and shape of the treatment zone after IRE, CT 3d rendering with the "Chebyshev Center Concept" implemented provides significantly different results compared with standard CT 3d analysis. Since the latter overestimates the size of the treatment zone, the "Chebyshev Center Concept" could be used for a more objective acute treatment control.
Available from: Jeong Min Lee
- "The single most important factor affecting the local tumor progression rate after RFA for hepatocellular carcinoma (HCC) or colorectal liver metastases (CRLM) could be the ablation of a tumor-free margin of hepatic parenchyma along the tumor margin as well as in the tumor itself (4-7). When the thickness of the ablative margin is evaluated by CT image fusion, a margin of 3-5 mm to 1 cm appears to be associated with a lower rate of local tumor progression after percutaneous RFA of HCC or CRLM (5, 6, 8, 9). Most clinically available electrodes, including internally cooled electrodes, multi-tined, expandable needle electrodes, and perfusion electrodes induce coagulation necrosis in the range of 3-4 cm in diameter after only a single ablation (10). "
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ABSTRACT: To compare the in-vitro efficiency of dual-switching monopolar (DSM) radiofrequency ablation (RFA) using a separable clustered electrode (Octopus® electrodes) with consecutive monopolar (CM) and switching monopolar (SM) RFA techniques to create an ablative zone in the explanted bovine liver.
For DSM-RFA, we used a prototype, three-channel, dual generator RFA Unit and Octopus® electrodes with three, 17 gauge internally cooled electrodes. The RFA Unit allowed simultaneous radiofrequency (RF) energy delivery to two electrodes of the Octopus® electrodes as well as automatic switching among the three electrode pairs according to the impedance changes. RF energy was sequentially applied to one of the three electrodes for 24 minutes (group A; CM mode, n = 10) or alternatively applied for 12 minutes (group B; SM mode, n = 10) or concurrently applied to a pair of electrodes for 12 minutes (group C; DSM mode, n = 10) in explanted bovine livers. Changes in the impedance and current during RFA as well as the dimensions of the thermal ablative zones were compared among the three groups.
The mean, delivered RF energy amounts in groups A, B, and C were 63.15 ± 8.6 kJ, 72.13 ± 5.4 kJ, and 106.08 ± 13.4 kJ, respectively (p < 0.001). The DSM mode created a significantly larger ablation volume than did the other modes, i.e., 68.1 ± 10.2 cm(3) (group A), 92.0 ± 19.9 cm(3) (group B), and 115.1 ± 14.0 cm(3) (group C) (p < 0.001). The circularity in groups A, B, and C were 0.84 ± 0.06, 0.87 ± 0.04 and 0.90 ± 0.03, respectively (p = 0.03).
DSM-RFA using Octopus® electrodes can help create large ablative zones within a relatively short time.
Available from: ajronline.org
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ABSTRACT: The objective of our study was to evaluate the feasibility rate and the reasons for infeasibility of percutaneous radiofrequency ablation of hepatocellular carcinomas (HCCs) at planning sonography.
We retrospectively evaluated 248 patients who had been referred for planning sonography at our department between October 2005 and February 2006. We reviewed the radiologic reports of 256 planning sonography examinations in terms of the rate of feasible cases and the reasons for infeasibility. The reasons for infeasibility were classified in six categories: an inconspicuous tumor, an inadequate electrode path, an organ vulnerable to collateral thermal damage, a tumor that was too large or too many tumors, and a high risk of the heat sink effect. In addition, we assessed the treatment modality for the patients who were determined to have HCCs for which percutaneous radiofrequency ablation was not feasible.
In 141 (55%) of the 256 planning sonography examinations, percutaneous radiofrequency ablation was feasible. The remaining 115 (45%) planning sonography examinations revealed that radiofrequency ablation was not a feasible procedure. The reasons for infeasibility included an inconspicuous tumor in 77 patients (55.8%), an inadequate electrode path in 33 patients (23.9%), an organ vulnerable to collateral thermal damage in 14 patients (10.1%), a tumor that was too large or too many tumors in eight patients (5.8%), a high risk of the heat sink effect in five patients (3.6%), and a portal vein thrombosis in one patient (0.7%). One reason for infeasibility was found in 96 patients, two reasons in 19 patients, and four reasons in one patient. Seventy (61.9%) of 113 patients for whom radiofrequency ablation was not feasible underwent transcatheter arterial chemoembolization as an alternative treatment.
In approximately half of the patients for whom percutaneous radiofrequency ablation of HCC is requested, the procedure is not feasible, mainly due to inconspicuous tumors, at planning sonography. Additional objective criteria for assessing the feasibility of radiofrequency ablation and therapeutic strategies according to the reasons for infeasibility should be investigated further.
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