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Editorial |
1 Department of Radiology, Boston University Medical Center, 88 E Newton St., Atrium 2, Boston, MA 02118.
Received February 13, 2006; accepted after revision February 13, 2006.
Address corresondence to B. C. Lucey.
Keywords: ablation • interventional radiology • radiofrequency
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The early articles reporting radiofrequency ablation in the liver were published in the early 1990s [1-3]. These studies set the stage for the procedure, but even these reports are buried among the multitude of radiofrequency ablation articles dedicated to cardiac ablations at that time. Reports of tumor ablation in experimental animal studies constituted most of the radiofrequency ablation articles until the past few years. Now it is barely possible to read a copy of a major radiology journal and not see at least one report devoted to clinical tumor ablation with radiofrequency. The literature on radiofrequency ablation has evolved from descriptions of technique and modifications, early clinical results, complications, and longer-term follow-up, to expansion of indications and finally to the "pearls and pitfalls" style of articles.
What becomes apparent and is clearly illustrated in the contents of this supplement is that increasing emphasis is being placed both on expanding the indications of radiofrequency ablation and on ensuring the safety of the procedure. Lesions that would not previously have been considered potential candidates for ablation are now being treated. This can be seen in the article by Hirooka et al. [4] that describes the use of virtual sonography for procedure guidance for lesions not detectable on CT. Kim et al. [5] and Cho et al. [6] refined radiofrequency ablation for use in high-risk patients with decompensated cirrhosis and patients with subcapsular liver masses, respectively, and Buy et al. [7] apply radiofrequency ablation in patients with high-risk spinal and paraspinal neoplasms.
Safety issues were also addressed in this issue, as evidenced by the use of dextrose as a protector against unintended thermal injuries in the article by Laeseke et al. [8]. This focus on safety, more than anything else, shows the emergence of radiofrequency ablation in mainstream radiology practice. Radiofrequency ablation is no longer the preserve of a minority of intrepid pioneers but now must be proven to be not only effective but also safe.
Given the wide dissemination of radiofrequency ablation techniques and applications in a relatively short time, it is understandable that differences in terminology would arise when describing the procedure and follow-up of patients, particularly in establishing what constitutes a treatment session and what constitutes successful or failed treatment. These differences can result in difficulty in standardization of methods and the subsequent evaluation of treatment results. As a result, a more formal International Working Group on Image-Guided Tumor Ablation was established in the late 1990s, comprising most of the major researchers in the radiofrequency ablation world, for standardization of terms and reporting criteria. This group published its recommendations in 2003 [9], and the recommendations were updated in 2005 and published simultaneously in two major radiology journals [10, 11]. The establishment of this working group is an example of the world radiology community identifying an area of opportunity and responding rapidly to evolving information. Publication of these recommendations has resulted in a clear improvement in the reporting of radiofrequency ablation studies, although full uniformity in study design and reporting has not yet been achieved.
What is most striking about radiofrequency ablation is the variety of valid clinical applications that have been developed in such a short time. From initial use as a treatment for hepatocellular carcinoma and then for hepatic metastases from colorectal carcinoma and neuroendocrine tumors, radiofrequency ablation was soon found to be of value for the local control of a multitude of other malignancies. Radiofrequency ablation of renal cell carcinoma has yielded excellent results [12], and it is also now a well-established option available for treating certain non-small cell lung carcinomas [13, 14], again with excellent preliminary results. Other malignancies treated with radiofrequency ablation include adrenal tumors [15], painful bone metastases [16], and even some breast carcinomas [17]. Some of these indications are well established and some remain controversial, but final judgment of each indication must be reserved until radiofrequency ablation proves itself individually in each case.
In the context of managing various neoplasms, radiofrequency ablation has assumed varying roles. Radiofrequency ablation does not promise to cure cancer. Although this may be expected with some renal cell carcinomas and possibly non-small cell lung carcinomas, in patients with hepatocellular carcinoma radiofrequency ablation is in essence a bridge to a liver transplantation rather than a cure; and in patients with hepatic metastases, prolonging disease-free survival with a reasonable quality of life is the goal. Radiofrequency ablation to date has been extremely successful in a short time in achieving these goals.
Debate remains, however, as to who should be performing radiofrequency ablation. In a radiology department, should the procedure be performed by interventional radiologists or body imagers? Should liver and kidney radiofrequency ablation be performed by abdominal radiologists, lung radiofrequency ablation by chest radiologists, and bone radiofrequency ablation by musculoskeletal radiologists? Another question is, what types of radiology practices should perform radiofrequency ablation? Without a doubt, most academic centers should now be offering this service. Larger established private practices affiliated with hospitals with sufficient manpower could also provide the service. However, it is doubtful if smaller private practices are in a position to offer radiofrequency ablation. The procedure is time-consuming, and to do it well requires experienced administrative and nursing staff. These questions have no right answer; the answer depends on the local practice in each individual radiology department.
In developing a successful radiofrequency ablation program, it will help to have dedicated formal clinic-type consulting rooms. Here, the radiologist performing the procedure can meet with the patient and family beforehand to discuss the case in detail, answer questions, and obtain informed consent. This is, after all, the treatment of cancer and is not a matter to be rushed into or discussed in a busy hallway. Such a preliminary interview will avert the pressure of detailed discussion and consent issues at the moment of the procedure itself. In addition, the clinic environment is an excellent setting for arranging follow-up imaging in these patients, which is all-important in identifying the degree of success of the radiofrequency ablation. Establishing such an interventional clinic helps the radiology practice to stand on an equal footing with physicians who refer their patients for radiofrequency ablation and shows a desire to take responsibility for total management of each patient's problem. This latter is important because interventional radiology as a specialty has always been under threat from members of other specialties who attempt to perform procedures that were often developed by interventional radiologists.
Radiofrequency ablation has become a touchstone of the recently developed notion of a new subspecialty of radiology—that is, interventional oncology. Establishing such a new subspecialty puts forward a belief in a total care concept for imaging-guided procedures for patients with cancer. These procedures would include all imaging-guided procedures specifically related to both the diagnosis and treatment of cancer. Interventional radiologists specializing in oncology practices would perform these procedures, with the range of procedures potentially crossing several well-established boundaries in many departments. However, although the concept of an interventional oncologist is a laudable one, it is difficult to see how this could be practicably achieved other than in a small number of highly specialized, high-volume cancer centers.
Given the relative ease with which radiofrequency ablation has permeated daily clinical practice, it is important to guard against too liberal an application of radiofrequency ablation in patient management. Poor patient selection and poor outcomes lead to a long-term rejection of a technology. This will not benefit radiology. It is vital for radiologists performing radiofrequency ablation to explain that it may be a treatment technique complementary to more conventional methods, including surgery, radiation therapy, and chemotherapy. Therefore, medical oncologists and radiation therapists should not fear radiofrequency ablation as a competing technique but should embrace it as an addition to the medical armamentarium. Indeed, the combination of chemoembolization and radiofrequency ablation has been reported [18], as have the use of brachytherapy with radiofrequency ablation [19] and radiofrequency ablation after surgical resection [20, 21]. It may be that in some way, radiofrequency ablation has synergistic effects with other treatment techniques—effects that are not independently related to the two treatments.
What, then, is the future of radiofrequency ablation? Should the focus be on expanding the clinical indications? Should it be to create the potential for larger areas of ablation? Should we be attempting to more perfectly control the area of ablation, or should we be looking for greater long-term success in the tumors we ablate? I believe that although these are all worthy goals to improve the techniques of radiofrequency ablation, our main focus needs to be concerned with the patient, both with careful patient selection and long-term patient outcome. We need to be able to better identify those patients who will benefit from radiofrequency ablation and show that the procedure has indeed benefited the patient. Both of these goals will require long-term follow-up and well-documented details of technique and patient selection. These details will best be obtained by large multicenter controlled trials. The challenge facing the radiology community is to establish large multicenter trials for each and every indication for radiofrequency ablation, with rigorous entry criteria and end points established in each limb of the trial.
Today there are competing techniques for radiofrequency ablation in the percutaneous management of neoplasms. More technologies can be expected over the coming years. Even if radiofrequency ablation can be shown to have a similar long-term outcome to resection, and even if radiofrequency ablation becomes a first-line treatment for patients with small hepatic, renal, or lung tumors, competing technologies may ultimately replace radiofrequency ablation if they are subsequently proven to be superior. History has shown that any technology has a limited shelf life before its inevitable replacement. The future of radiofrequency ablation is now.
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