Step 1
Surgical Anatomy
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Surgical resection is the mainstay of treatment for patients with early-stage lung cancer.
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Radiofrequency ablation (RFA) is an appropriate alternative for patients who either refuse surgery or have a prohibitive risk for surgical resection. In our experience many patients who are considered “inoperable” on the basis of poor pulmonary function are acceptable candidates for a thoracoscopic wedge resection, a procedure that has a superior local control rate compared with RFA.
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Patients should be adequately staged before considering RFA. Those with suspected nodal involvement on the basis of computed tomography (CT) or positron emission tomography criteria should undergo invasive staging (either mediastinoscopy or endobronchial ultrasound) before RFA is offered to treat the primary lesion.
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Before RFA is done, tissue confirmation of malignancy is mandatory. A CT-guided needle biopsy can be scheduled at the same setting as the planned RFA. Ablation of pulmonary nodules without a tissue diagnosis will lead to unnecessary treatment of patients with benign disease.
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Characteristics of the primary tumor are critical for selecting patients for RFA. For example, tumors larger than 5 cm in diameter should not be treated with RFA given the high recurrence rate when tumors of this size are ablated. In addition, significant hemoptysis can occur after RFA in patients with central tumors.
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Patients with metastatic disease to the lungs can be considered for RFA, assuming they are not operative candidates and meet the accepted criteria for metastasectomy (e.g., good control of the primary tumor with limited disease in the chest). Patients with multiple pulmonary metastases should not be offered RFA unless all sites of disease are treatable.
Step 2
Preoperative Considerations
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RFA causes coagulative necrosis by heating tissue to a temperature of 60°C. RFA energy is produced by a generator, is dispersed through the active electrode of the RFA probe, and then travels to a “dispersive electrode” (the Bovie pad). The target tissue is heated as energy alternates between the probe and the dispersive electrode.
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Currently three probes are available for RFA of pulmonary lesions.
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Boston Scientific (Natick, MA): This probe consists of expandable tines that assume an umbrella configuration. RFA energy is dispersed throughout the length of each tine. The tines can be expanded to a maximum length of 5 cm. Proper use of this probe will consist of deploying the probe into the center of the target lesion. The tines are then sequentially expanded so the entire volume of the lesion is treated ( Fig. 13-1 ). This probe is impedance-based. Heating of the target tissue is maintained until the impedance measured across the probe rises to the appropriate level. Impedance, a measure of resistance to flow of RFA energy, will reach a plateau level as the tissue is coagulated and unable to maintain conduction.
Figure 13-1
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RITA (Mountainview, CA): The design is similar to the Boston Scientific probe. However, the RITA probe is temperature-based. In this system, the tissue is considered ablated once it has been heated to a target temperature (usually 90°C) for a specified amount of time.
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Valley Laboratory (Boulder City, CO): Unlike the Boston Scientific and RITA systems, this probe does not have expandable tines. Instead, the probe consists of either a single needle or an assembly of three needles that are placed within the tumor ( Fig. 13-2 ). The distal 2.5 cm is uninsulated and represents the active portion of the electrode. The probe is continuously irrigated with ice water and is often referred to as a “cooltip” probe. Because the probe does not have tines, the distal end of the probe should be deployed to the depth of the target lesion. A 4.5-cm zone of ablation will extend around the probe. The Valley Lab probe is temperature-based.
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