Chapter 154 Jeffrey P. Guenette and Damian E. Dupuy Lung cancer is the most common primary cancer, with over 220,000 new cases in 2010, and is the most common cause of cancer death, with nearly 160,000 deaths per year.1,2 Surgery is the mainstay of treatment for primary lung cancer, but it is estimated that over 15% of all patients and 30% of patients over age 75 with stage I or II non–small cell lung cancer (NSCLC) are medically inoperable.3 Moreover, local therapy with external beam radiation has shown a best 2-year overall survival of only 51%,4 with newer stereotactic body radiotherapy techniques (i.e., stereotactic body radiation therapy [SBRT]) showing 3-year survival rates of 42% to 60% for early-stage, medically inoperable NSCLC.5,6 Pulmonary metastatic disease is generally an indicator of wide disease dissemination requiring systemic therapy, but when a finite number of metastatic deposits exist in the lung, resection may improve prognosis for certain pathologies, including primary sarcoma, renal cell carcinoma, colorectal carcinoma, and breast carcinoma.7–12 In the case of colorectal carcinoma with isolated pulmonary metastases, 5-year survival rates can exceed 50%.12 Again, as with primary lung cancer, pulmonary metastases are often inoperable owing to patients’ poor cardiopulmonary function, advanced age, and other medical comorbidities. Electromagnetic (EM) energy takes form as oscillating perpendicular waves of electrical and magnetic fields traveling at the speed of light. EM wave frequencies range from 10 Hz (waves per second) to 1024 Hz, with radio waves having frequencies as low as 104 Hz, followed by microwaves, infrared waves, visible light, ultraviolet waves, x-rays, and gamma rays in increasing order of wave frequency.13,14 Three of the four thermal ablation modalities utilize waves along this spectrum. Radiofrequency ablation (RFA) is the most widely used ablation modality for the treatment of solid tumors; its safety has been firmly established in solid malignancies of the lung (Fig. 154-1 and Table 154-1), liver, bone, breast, kidney, and adrenals.15 With this technique, an active RF electrode (applicator) is placed in the tumor under imaging guidance, and a grounding pad (reference electrode) is applied to the chest wall opposite the applicator or on the thigh. Most clinical RFA electrodes emit radio waves in the range of 375 to 500 kHz, generating electrical field lines between the applicator and reference electrode that oscillate with the alternating current. These fields result in collision of electrons with molecules adjacent to the applicator, generating frictional heat.16 Temperatures exceeding 60°C, regardless of the heating source, induce cell cytotoxicity via thermolabile protein denaturation,17 and this temperature is generally considered the baseline for inducing immediate coagulative necrosis. Care is taken to keep the electrode tip temperature below 100°C to avoid charring and vaporization, which occur at 110°C, because these processes increase electrical impedance and inhibit heat dissipation to surrounding tissue.18 The goal is to ablate an appropriate circumferential margin: 95% of microscopic neoplastic extension is within a margin of 8 mm from the tumor border for adenocarcinoma and 6 mm for squamous cell carcinoma.19 TABLE 154-1 Outcomes from Leading and Supportive Studies Conducted on Various Lung Ablation Modalities
Lung Ablation
Basic Biophysics of Lung Ablation
Radiofrequency Ablation
