Lung Ablation

Chapter 154

Lung Ablation

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.

Image-guided thermal ablation is an increasingly studied and used treatment for both cure and palliation of primary and secondary lung cancer. The technique has been used for a little over a decade and has been shown to be safe and effective in treating a variety of solid tumors including many in the lung, liver, kidney, breast, bone, and adrenal gland. It may be used in conjunction with radiotherapy and systemic chemotherapy and is relatively low cost. Thermal ablation modalities include radiofrequency, microwave, laser, and cryotherapy. Randomized controlled clinical trials have not yet been conducted to establish efficacy of thermal ablation alone, in combination with, or relative to other established treatments of lung neoplasms. However, an increasing number of single and multicenter cohort studies have consistently established the safety and suggest efficacy for medically inoperable disease. The remainder of this chapter highlights the basic biophysics underlying thermal ablation modalities, specifically within the unique anatomy and physiology of the lung, the understood safety and efficacy of thermal lung ablation given our experience to date, newly introduced advances in thermal lung ablation techniques, and the current role of thermal ablation in the treatment of lung cancer.

Basic Biophysics of Lung Ablation

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

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

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Dec 23, 2015 | Posted by in INTERVENTIONAL RADIOLOGY | Comments Off on Lung Ablation
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Author Year No. Patients No. Tumors Notable Findings
Radiofrequency Ablation
Hiraki et al.49 2011 50 52 primary
Palussiere et al.39 2010 127 210 Probability of survival 72% at 2 years, 60% at 3 years, 51% at 5 years
Zemlyak et al.50 2010 64
25 resection
12 RFA
27 cryo
Huang et al.35 2010 329
237 primary
92 mets
Beland et al.51 2010 79 79 primary
Lanuti et al.52 2009 31 34 primary
Lencioni et al.53 2008 106 183
33 primary
150 mets

Pennathur et al.54 2007 19  
Simon et al.55 2007 153 189
116 primary
73 mets

de Baere et al.56 2006 60 100
Dupuy et al.57 2006 24  
Thanos et al.58 2006 22 22
14 primary
8 mets

Yan et al.59 2006 55 55 mets
Fernando et al.60 2005 18
5 primary
13 mets
Akeboshi et al.61 2004 31 54
13 primary
41 mets

Kang et al.62 2004 50
23 primary
27 mets
Lee et al.63 2004 30 32
5 mets

Yasui et al.64 2004 35 99
3 primary
96 mets

Herrera65 2003 18 33
Microwave Ablation
Wolf et al.66 2008 50