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Original Articles: General Thoracic

Invited Commentary

Department of Surgery, University of Michigan Medical Center, TC2120G/5344, 1500 East Medical Center Dr, Ann Arbor, MI 48109

(Email: andrwchg{at}umich.edu).

Radiofrequency ablation (RFA) for the treatment of either primary or metastatic lung cancer has been used as an alternative, particularly for patients who have limited pulmonary reserve or who are otherwise considered to be "medically inoperable." Although this emerging technology is the focus of an ongoing cooperative group pilot trial (American College of Surgeons Oncology Group Z4033) for patients with early stage nonsmall cell lung carcinoma, few studies have validated this technique biologically. Schneider and colleagues [1] present their study of intraoperative RFA with an "ablate and resect" approach for the treatment of pulmonary metastases. The purpose of their study was to evaluate the histologic changes in metastatic tumors after intraoperative RFA, with attention to assessing cellular viability at the ablation zone margins. Cellular viability at the tumor margins was determined by two methods: (1) determination of mitochondrial staining by mitochondrial-specific antibody and (2) assessment of nicotinamide adenine dinucleotide (NAD+) reduction by vital staining. Of 24 patients enrolled in the study, 6 were excluded, including 2 patients in whom the ablation probe placement was not within the center of the targeted lesion.

With tumors ranging in size from 7 mm to 25 mm among the patients consenting to this study, only 39% (7 patients) were found to have complete tumor ablation with neither detection of mitochondrial staining nor NAD+-reducing activity noted. Near complete ablation (>90%) occurred in an additional 50% (9 patients) of centrally-treated tumors, with incomplete ablation occurring in 2 of the 18 patients studied. Had the 2 patients who were excluded because of tangential probe placement been included in histologic analysis, then incomplete ablation would have occurred in 4 of 20 patients. However, this study was not a trial of RFA efficacy, but rather a study of histopathologic correlation. The authors' approach of determining cell viability by mitochondrial staining and NAD+ activity provides potentially more accurate assessment of tumor viability than standard histologic techniques. Furthermore, because tumors were resected immediately after ablation, continued cell death still might have occurred in situ, as discussed by the authors. Other measures discussed by Schneider and colleagues [1], particularly terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick end labeling (TUNEL) staining, have been evaluated. Most recently, for example, Clasen and colleagues [2] evaluated percutaneous RFA followed by scheduled resection 3 days post-ablation. Of 11 tumors treated in 9 patients, 10 had evidence of tumor necrosis by TUNEL staining and electron microscopy, even though hematoxylin and eosin staining indicated preserved tissue architecture. In addition, there was only minimal to no margin of tissue damage around 2 ablated tumors. Both of these reports demonstrate that validation of nonsurgical ablative technology should include not only standard histologic studies but also evaluation of cellular viability and/or pathomorphology.

Ultimately the efficacy of RFA will depend on long-term oncologic outcomes. The authors adopt an appropriate cautionary tone regarding RFA for pulmonary metastasectomy. Their findings demonstrate that ablative techniques, such as RFA, even when properly targeted, still can result in incomplete ablation. Therefore, such an approach should be reserved only for patients considered "medically inoperable." Surgical metastasectomy, when oncologically and medically feasible, remains the preferred approach.

	References

Top References

 

1. Schneider T, Warth A, Herpel E, et al. Intraoperative radiofrequency ablation of lung metastases and histologic evaluation Ann Thorac Surg 2009;87:379-384.[Abstract/Free Full Text]
2. Clasen S, Krober SM, Kosan B, et al. Pathomorphologic evaluation of pulmonary radiofrequency ablation Cancer 2008;113:3121-3129.[Medline]

This Article Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Add to Personal Folders Download to citation manager Author home page(s): Andrew C. Chang Permission Requests Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Chang, A. C. Search for Related Content PubMed PubMed Citation Articles by Chang, A. C. Related Collections Lung - other Related Article