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Rizzoli Orthopedic Institute Bologna 40136, Italy
We read the article by Neeman et al. [1] with great interest. They described a precise and detailed treatment of recurrent chordoma by radiofrequency thermal ablation.
The article was particularly interesting because it proposed a new application of radiofrequency thermal ablation treatment in the musculoskeletal system. Recurrent chordoma is uncommon, but despite radical ablative surgical treatment, it is subject to local and regional recurrence, which requires repeated surgery [2, 3].
Since June 2001, we have been using radiofrequency thermal ablation to
treat osteoid osteomas located not only in the appendicular skeleton and
pelvis (108 patients) but also in the axial skeleton (four patients). We have
applied radiofrequency thermal ablation to other local benign and malignant
lesions, including one in a patient with recurrence in the soft tissues of
sacral chordoma [4,
5], because of the anatomic
pathologic characteristics and evolution of some musculoskeletal lesions. We
consulted with orthopedic colleagues and obtained the patient's informed
consent. A needle biopsy was performed under general sedation and local
infiltration anesthetic before the thermal ablation procedure because the
lesion was close to (10 mm) the posteriorly herniated colon. Radiofrequency
thermal ablation was performed using a Miras TAG 100 W generator and needle
electrode (Invatec Italy). Radiofrequency energy was delivered gradually (15
min; maximal power, 18 W; maximal resistance, 100 
), and a temperature
of 70°C was maintained for approximately 8 min. The procedure was fairly
well tolerated by the patient.
At 4 months' follow-up, a CT scan with contrast medium showed a lesion with decreased volume that included small areas of necrosis and fibroadipose involution but with no areas of contrast enhancement.
Therefore, we think the application proposed by Neeman et al. [1] is of extreme interest, because it opens the way for applying radiofrequency thermal ablation to local or regional recurrences of musculoskeletal diseases with "local malignity" that otherwise require repeated ablative surgical interventions that affect the patient's quality of life.
References
National Institutes of Health Bethesda, MD 20892
We read with interest the letter by Dr. Albisinni et al. in response to our article [1] regarding radiofrequency ablation of local or regional recurrences of slow-growing musculoskeletal tumors. We applaud their fine work and agree that thermal ablation holds promise for palliation of these tumors. Thermal ablation provides a minimally invasive treatment option for recurrences that does not carry the long recovery times required by repeated surgery. The impact of repeated surgical procedures on quality of life is often underestimated.
We have treated three patients with chordoma with radiofrequency ablation, all with similar shorter treatment times and relatively lower power and current settings than are typically used to ablate liver tumors. We have seen a wide variety of thermal effects in radiofrequency ablation of different histologies, and we believe that there are inherent differences in thermal and electrical conductivity between different tumor types. The fast ablation time for chordoma may also result in part from its water content or relative lack of vascularity. We have noticed in ablating 25 adrenocortical carcinoma metastases that their tissue is also quite responsive to low-current and short-treatment-time settings even when the tumor is intrahepatic.
We have an active protocol for studying the palliative effects of radiofrequency ablation on painful soft-tissue tumors and plan to study the effects on unusual bone tumors, such as painful fibrous dysplasia.
We are developing methods to study tissue-specific dielectric properties using a network analyzer and a custom-fabricated capacitor. These data may also be important for modeling the heat effects on tissue for treatment planning and algorithm optimizing. We plan to develop tissue-specific rules for radiofrequency ablation to enter into the generator and use modules that will prescribe adjustments in the treatment algorithms.
We are glad that the authors have shared their experience. A Web-based registry to document differences in treatment times, power levels, and current settings might be a useful source for other physicians encountering similar histology and location.
References
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