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INTRODUCTION

Lung cancer is the leading cause of cancer death for both men and women worldwide.1 The introduction of lung screening programs worldwide has increased the diagnosis of early-stage lung cancer in high-risk populations. Surgical resection remains the gold standard treatment for early-stage lung cancer. Yet, only one-third of patients diagnosed with lung cancer are stage appropriate for surgical therapy.2 Further, the growing number of elderly people in the United States and other Western countries has caused an increase in the number of patients with comorbidities, making primary surgical and curative therapy more complicated.

The lung is also a frequent site of metastasis, with pulmonary metastases occurring in 30% of all malignancies.1 However, a significant proportion of patients are unable or unwilling to undergo surgery. For these patients, ablative therapy may be an option for localized treatment. The technique of percutaneous tumor ablation has developed through the introduction of multiple modalities, including radiofrequency ablation (RFA), microwave ablation (MWA), cryoablation, irreversible electroporation (IRE), and a highly efficient radiation delivery method represented by stereotactic body radiation therapy (SBRT).

RADIOFREQUENCY ABLATION

Radiofrequency energy, introduced by William T. Bovie, was first used in surgery with the application of cauterization in 1926. Because pulsed electrical current was shown to cause coagulation in tissue and continuous current resulted in the cutting of tissue, the technique afforded precision cuts with minimal blood loss.3 Percutaneous RFA was first reported in 1990 for liver tumor ablation.4 Since then, the indications have expanded to other organs such as kidney, bone, and lung. The mechanism of action and outcomes of treatment are reviewed in this chapter.

MECHANISM OF ACTION

RFA refers to the therapeutic use of electromagnetic radiation (EMR) for the selective destruction and removal of biologic lesions. EMR exhibits wave-like behavior corresponding in magnitude to the light spectrum (e.g., microwaves, radio waves, infrared, visible light, ultraviolet, x-rays, gamma rays). RFA uses energy at the frequency and length of radio waves (2–300 Hz).5 A circuit is created that flows from the tip of the electrode, to a large, diffuse grounding pad placed over the patient’s thighs, and then to an external generator. The small cross-sectional area of the electrode creates a surrounding region of high energy flux. The molecules next to the electrode, usually water, align with the direction of the current. The rapidly alternating current causes the adjacent molecules to vibrate. Molecules farther away from the probe are affected by the other vibrating molecules. The frictional loss of energy between molecules results in a temperature increase.6 The electrode itself is not a source of heat but creates the electromagnetic field that causes molecular movement and, hence, heat generation.

Temperature control is an important issue in RFA. Temperature must be managed to allow energy to be conducted through the tissues. Excessive energy can cause the buildup of ...

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