Re: Assessment of Viable Tumour Tissue Attached to Needle Applicators after Local Ablation of Liver Tumours

RITA XL (n = 14) electrodes [6] . 13/68 (19%) specimens were positive for Ki67, 12/54 (22.2%) from the Leveen and 1/14 (7%) from the RITA electrode. This difference was not statistically significant (p = 0.27). Should this trend remain the same, a statistically significant difference could be established if the population was 250. We have certain questions regarding the methodology of Snoeren et al. [1] : (1) Is it possible that any cells reacting to the G6PD were normal viable hepatocytes and not tumor? (2) Macroscopic tissue adherent on RITA electrodes was seen in 87.5% cases. Did all these specimens contain completely destructed, non-identifiable cells? Were there any nests of identifiable tumor cells with or without changes of thermal injury? (3) It appears that tissue was found in 7/8 cases (87.5%) treated with the RITA electrode. Is it possible that the differences in the incidence of viable tumor cells between electrodes would be different with the addition of more cases? (4) The inability to resect with a clear, tumor-free margin, and multifocal and extrahepatic disease were indications for ablation. Was the ratio of patients with these factors similar between the Dear Sir, We have read with great interest the paper by Snoeren et al., entitled ‘Assessment of viable tumour tissue attached to needle applicators after local ablation of liver tumours’ [1] . The authors commented that the finding in our earlier publication [2] where intact tumor cells were detected by simple HE examinations on tissue extracted on the RITA Starburst XL electrode after ablation of liver malignancies is remarkable. This finding was not in accordance with their findings where viable tumor was only found on the Leveen Radiotherapeutics device [1] . In order to improve the limitations of morphologic stains alone in our initial study [2] , we performed evaluation of fixed specimens with proliferation marker Ki67 [3, 4] and apoptosis marker caspase 3 [5] . This study [6] demonstrated that tumor cells positive for Ki67 carry a risk of approximately 6 times for local tumor progression (LTP) when compared to those that are Ki67negative (hazard ratio 5.9, 95% CI 2.4– 14.5, p ! 0.001). Furthermore, for the subset of tumors under 3 cm in largest diameter, this risk is over 10 times for the Ki67-positive tumor cells when compared to those that test negative (hazard ratio 10.1, 95% CI 1.7–57.5, p = 0.009). In this study, we collected specimens after RF ablation with the Leveen (n = 54) and the Published online: November 13, 2009