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Musculoskeletal Cancer Treatment of Bone Tumours by Radiofrequency Thermal Ablation – Beyond the Osteoid Osteoma Fernando Ruiz Santiago, 1 Luis Guzmán Álvarez 2 and María del Mar Castellano García 3 1. Head, Department of Musculoskeletal Radiology; 2. Physician, Musculoskeletal Section, Department of Radiology, Traumatology Centre, Hospital Universitario Virgen de las Nieves, Spain Abstract Percutaneous radiofrequency thermal ablation (RFTA) is a modality of therapy suitable in treating different kind of tumours and tumour like conditions. The effects are based on converting radiofrequency into heat, leading to necrosis of the target area. Today it is considered the treatment of choice for osteoid osteomas but it has also yielded satisfactory results in other kind of neoplasms, either benign or malign. This review includes some basic technical considerations of the procedure and describes its applications in treating bone and soft tissue tumours, as adjuvant therapy or as unique technique, with curative or palliative intention. These tumours include benign conditions (chondroblastoma, enchondroma, osteoblastoma, haemangioma, eosinophilic granuloma, aneurismal bone cyst, giant cell tumour, desmoid tumour) and malign ones, mainly soft tissue and bone metastases. Keywords Bone neoplasms therapy, soft tissue neoplasms therapy, percutaneous radiofrequency ablation, bone tumours, intervention Disclosure: The authors have no conflicts of interest to declare Received: 4 February 2012 Accepted: 1 October 2012 Citation: European Oncology & Haematology, 2012;8(4):228–31 Correspondence: Fernando Ruiz Santiago Julio Verne 8, 7B 18003 Granada, US. E: ferusan12@gmail.com Thermal methods for tumours treatment (radiofrequency, laser, microwave, cryoablation, high intensity focused ultrasound) have become important palliative, and in some cases curative, modalities. Among these techniques, percutaneous radiofrequency thermal ablation (RFTA) has attained widespread use. RFTA bases its effect on cellular damage secondary to converting radio waves into heat in a circumscribed body area. At present, this constitutes the standard initial procedure for a definitive curative treatment of osteoid osteoma. Other benign and malign bone or soft tissue tumours and pseudotumours are also suitable for RFTA. 1 In these cases treatment is intended to be palliative or curative. Curative treatment implies that the tumour has been completely ablated. Palliative treatment aims to reduce symptoms and debulking tumour mass. 2 This article aims to review the usefulness of radiofrequency thermal ablation in other tumour conditions different of osteoid osteoma. Technical considerations. The most widely used radio frequency (RF) devices for musculoskeletal applications are monopolar systems. The electric circuit is formed by using an electric generator connected to a probe or active electrode (antenna) placed inside the lesion and a large grounding pad, or dispersive electrodes placed over the skin. An alternating electric current from the RF generator flows through the electrode non insulated active tip into the patient and out through the grounding pads back to the generator. Heat is produced by resistive forces that produce ionic and molecular agitation in the tissues surrounding the electrode tip during attempts by the radio waves to return to the grounding pads 3 (see Figure 1). 228 The temperature reached in the target tissue decreases directly proportional to the distance from the electrode (1/r 2 ; r = radius of the active tip). Therefore, necrosis is focused to the volume around the electrode, making heating induced damage remote to the source of heat rather unlikely. 4 The intrinsic properties of the targeted tissue, such as heat conductivity and convection, also influence the final volume of ablation. Thermal effect can be reduced by adjacent high-flow vascular structures which act as a cooling circuitry. Heat convection to adjacent blood vessels (‘heat sink’ effect) can serve to protect vascular integrity from thermal damage. 5 A rod electrode is more appropriate in bone tumour treatment because it can be inserted through a drilled hole. The distribution of heat around rod monopolar electrodes follows a cylindrical contour with rounded edges. Most heat generation is produced in tissues with lower resistance and tissue resistivity is much higher in cortical than marrow bone. Hence, cortical tissue is much more resistant to heating and has an insulating effect, when intact, protecting surrounding soft tissues and cartilage. 6 Internal cooling of the RF electrode is a strategy to increase energy application. Internal lumina enables a perfusion of the electrode shaft with saline or water, not in direct contact with patient tissues. Internal cooling of the needle allows increase generator output, while avoiding premature carbonisation around the probe that lead to insulation and energy decay. Subsequently, internal cooling prevents or delays a deleterious increase in circuit impedance. The combination of pulsed energy application and internal cooling leads to a synergistic increase of induced coagulation. Saline infusion has been shown to be effective in © TOUCH MEDICAL MEDIA 2012