The slide is titled "Lung Ablation" and serves as a title page for a presentation. It features a subtitle that provides an overview of interventional radiology techniques and supporting evidence related to lung ablation.

Lung Ablation

Interventional Radiology: Overview of Techniques & Evidence

Source: Chapter 104

--- Speaker Notes: Today I’ll be presenting Chapter 104 on Lung Ablation. We’ll review the biophysics of thermal ablation modalities, the clinical evidence supporting their use, emerging technical advances, and how ablation fits into the broader lung cancer treatment algorithm.

Lung cancer is the most common cancer and the leading cause of death, with many early-stage non-small cell lung cancer (NSCLC) patients being medically inoperable. Stereotactic body radiation therapy (SBRT) provides limited survival outcomes for these cases and plays a key role in treating pulmonary metastases.

Epidemiology & Rationale

• Lung cancer: most common cancer and leading cause of death

• Many early-stage NSCLC patients medically inoperable

• SBRT offers limited survival outcomes

• Key role in pulmonary metastases treatment

--- Speaker Notes: Lung cancer remains the most common primary cancer and leading cause of cancer death. Despite surgery being the gold standard, up to 30% of early-stage NSCLC patients—especially older patients—are medically inoperable. SBRT is useful, but survival remains limited. Ablation also plays a key role for selected pulmonary metastases, especially from colorectal cancer, renal cell carcinoma, sarcoma, and breast cancer.

Thermal ablation modalities include Radiofrequency Ablation (RFA), which uses frictional heating from RF waves; Microwave Ablation (MWA), which oscillates water molecules to create larger treatment zones; and Laser Ablation, employing infrared light to cause thermal injury in metastases. Cryoablation rapidly freezes tissue to induce necrosis through ice crystal formation, with the slide also covering basics of RF, microwave, and laser principles from the electromagnetic spectrum.

Overview of Thermal Ablation Modalities

• Radiofrequency Ablation (RFA): Frictional heating via RF waves

• Microwave Ablation (MWA): Oscillating water molecules for larger zones

• Laser Ablation: Infrared light for thermal injury in metastases

• Cryoablation: Rapid freezing induces ice crystal necrosis

• Electromagnetic Spectrum Basics: RF, MW, and laser principles

--- Speaker Notes: We use four thermal ablation modalities in the lung. RFA and microwave ablation are the most common, laser is emerging, and cryotherapy is increasingly used. Three modalities—RF, microwave, and laser—operate along the electromagnetic spectrum, while cryoablation works via rapid cooling.

Radiofrequency ablation uses RF waves at 375–500 kHz to generate frictional heating above 60°C, inducing coagulative necrosis in targeted tissues. To avoid charring and impedance rise, temperatures must stay below 100°C, with recommended ablation margins of about 8 mm for adenocarcinoma and 6 mm for squamous cell carcinoma.

Radiofrequency Ablation: Mechanism

• RF waves at 375–500 kHz

• Frictional heating >60°C induces coagulative necrosis

• Avoid >100°C to prevent charring and impedance rise

• Target margin: ~8 mm (adenocarcinoma), ~6 mm (SCC)

--- Speaker Notes: RF ablation generates frictional heat from alternating electrical currents. Temperatures above 60 degrees cause coagulative necrosis, but exceeding 100 degrees risks charring and increased impedance. Achieving circumferential margins of 6–8 mm is essential based on microscopic tumor spread.

The slide on RFA Devices outlines key examples, including the LeVeen system, which uses impedance-based energy monitoring; the StarBurst, featuring temperature-based control with saline perfusion; and the Cool-tip, which employs single or cluster electrodes with internal cooling. It notes the absence of head-to-head comparative trials among these devices.

RFA Devices

• LeVeen: impedance-based energy monitoring

• StarBurst: temperature-based with saline perfusion

• Cool-tip: single or cluster electrodes with internal cooling

• No head-to-head comparative trials

--- Speaker Notes: These are the three primary RFA systems. Each uses slightly different electrode configurations and energy monitoring strategies, but there are no comparative trials demonstrating superiority.

In radiofrequency ablation (RFA) of the lung, air acts as an insulator to concentrate energy on the tumor while airflow and perfusion form heat sinks that dissipate heat. The lung's limited water content can be mitigated by using saline perfusion to enhance effectiveness.

RFA in the Lung: Biophysics

• Air insulates, focusing energy in tumor

• Airflow and perfusion create heat sinks

• Limited water content; saline perfusion helpful

--- Speaker Notes: The lung is a unique environment: air acts as an insulator, concentrating heat within the tumor. However, airflow and perfusion dissipate heat around the tumor, making margin creation more difficult. Low water content can increase impedance, so saline infusion can be helpful.

Microwave ablation operates at frequencies of 900–2450 MHz, causing dipole rotation of water molecules to generate heat. This results in a larger active heating zone with reduced heat sink effects, enabling faster and larger ablations.

Microwave Ablation: Mechanism

• 900–2450 MHz frequency

• Dipole rotation of water molecules

• Larger active heating zone

• Less heat sink effect

• Faster and larger ablations

--- Speaker Notes: Microwave ablation heats tissue by oscillating water molecules. This produces a larger and more uniform ablation zone, is less affected by heat sinks, and allows simultaneous multi-antenna use. These advantages are especially relevant in aerated lung.

Microwave ablation (MWA) devices include six FDA-approved US systems operating at 915 or 2450 MHz frequencies. These devices feature shaft cooling for enhanced performance, produce larger and more spherical ablation zones, and offer improved control at tumor margins.

MWA Devices & Advantages

• Six FDA-approved US systems at 915 or 2450 MHz

• Shaft cooling systems for improved performance

• Larger, more spherical ablation zones

• Better control at tumor margins

--- Speaker Notes: There are multiple commercial systems with differences in frequency and cooling. Microwave lesions tend to be more predictable and spherical, which improves margin control compared with RFA.

Laser ablation, as described on the slide, utilizes an Nd:YAG laser at a 1064 nm wavelength, where photon absorption leads to thermal injury in targeted tissues. While its use is limited in the United States, European experiences highlight its application in treating metastases.

Laser Ablation

• Nd:YAG laser at 1064 nm wavelength

• Photon absorption causes thermal injury

• Limited use in the United States

• European experience treats metastases

--- Speaker Notes: Laser ablation uses monochromatic infrared light from an Nd:YAG laser. While it's not widely used in the US for primary tumors, European studies suggest it may offer durable control for metastatic disease.

Cryoablation employs argon gas to cool tissues to –140°C, forming intracellular ice crystals that induce necrosis. The process is enhanced by a freeze–thaw–freeze protocol, which triggers reperfusion injury leading to apoptosis and greater tissue destruction.

Cryoablation: Mechanism

• Argon gas cooling to –140°C

• Intracellular ice crystals cause necrosis

• Reperfusion injury induces apoptosis

• Freeze–thaw–freeze protocol enhances destruction

--- Speaker Notes: Cryoablation induces cell death through ice crystal formation and through endothelial injury during thawing. A freeze–thaw–freeze cycle enhances zonal tissue destruction. It is advantageous for tumors near critical structures due to the visible ice ball.

Cryoablation in the lung is unaffected by air in ice ball formation and offers excellent CT visualization for precise monitoring. It allows multiple probes to treat large tumors effectively and is particularly useful for those near the mediastinum or diaphragm.

Cryoablation in the Lung

• Air does not alter ice ball formation

• Excellent CT visualization of ice ball

• Multiple probes enable treatment of large tumors

• Useful for tumors near mediastinum or diaphragm

--- Speaker Notes: Unlike RF and MW, cryoablation is not hindered by air. The ice ball is easily visualized on CT, improving safety when treating tumors abutting critical structures.

For Stage IA NSCLC patients, the slide reports an 86% 1-year overall survival rate and a 36% 5-year overall survival rate. For patients with pulmonary metastases, it shows an 80% 1-year overall survival rate and a 17% 5-year overall survival rate.

Evidence Summary

• 86%: 1-Year OS

Stage IA NSCLC patients

• 36%: 5-Year OS

Stage IA NSCLC patients

• 80%: 1-Year OS

Pulmonary metastases

• 17%: 5-Year OS

Pulmonary metastases

--- Speaker Notes: Most evidence comes from RFA, showing promising survival in medically inoperable NSCLC and pulmonary metastases. Tumors under 3 cm have the best local control, while size >3 cm significantly increases recurrence risk.

The slide on complications lists common risks from the procedure, including pneumothorax at 19%, pneumonia at 4%, and hemoptysis or hemothorax at 3-4%. It also mentions COPD exacerbation and rare events such as tamponade, abscess, and bronchopleural fistula.

Complications

• Pneumothorax (19%)

• Pneumonia (4%)

• Hemoptysis/hemothorax (3–4%)

• COPD exacerbation

• Rare: tamponade, abscess, bronchopleural fistula

--- Speaker Notes: Complications are generally manageable, with pneumothorax being the most common. Severe complications are rare but reported in the literature.

The slide on Imaging Follow-up outlines benign patterns observed one year post-procedure, including fibrosis, nodule, cavitation, and atelectasis. It also highlights key indicators of recurrence, such as ground glass to solid transition, enlarging ablation zone, 10 mm nodular enhancement, and FDG activity.

Imaging Follow-up

• Benign 1-year patterns: fibrosis, nodule, cavitation, atelectasis

• Recurrence indicator: ground glass to solid transition

• Recurrence indicator: enlarging ablation zone

• Recurrence indicator: 10 mm nodular enhancement

• Recurrence indicator: FDG activity

--- Speaker Notes: Post-ablation imaging can show several benign patterns. What matters is change: new solid components, increasing enhancement, or FDG uptake suggest recurrence.

Recent advances in ablation techniques include bronchial occlusion to reduce the heat sink effect, arterial balloon occlusion to minimize perfusion cooling, and the combination of RFA with HDR brachytherapy to enhance efficacy. Additional innovations involve creating hydromediastinum to improve ablation zones and demonstrating feasibility in single-lung patients.

Advances in Techniques

• Bronchial occlusion reduces heat sink effect

• Arterial balloon occlusion minimizes perfusion cooling

• Combined RFA and HDR brachytherapy enhances efficacy

• Hydromediastinum creation improves ablation zones

• Ablation feasible in single-lung patients

--- Speaker Notes: Multiple innovative approaches are being explored to improve margin creation or allow treatment in anatomically challenging situations.

Surgery is the gold standard treatment for NSCLC, with ablation serving as a key option for medically inoperable stage I cases and limited pulmonary metastases. Ablation delivers outcomes comparable to SBRT while offering lower costs, repeatability, and reduced long-term toxicity.

Current Clinical Role

• Surgery remains the gold standard treatment

• Ablation for medically inoperable stage I NSCLC

• Ablation for limited pulmonary metastases

• Outcomes approaching those of SBRT

• Lower cost, repeatable, less long-term toxicity

--- Speaker Notes: Although surgery remains the gold standard, ablation plays a major role for medically inoperable patients and selected metastases. Recent data show outcomes approaching those of SBRT, with added benefits including repeatability and lower cost.

This conclusion slide highlights radiofrequency ablation as a safe and effective treatment option for selected patients, particularly yielding the best results for tumors smaller than 3 cm, while noting the availability of multiple complementary techniques and ongoing advances that enhance outcomes. It ends with a simple thank you.

Conclusion

• Safe, effective modality for selected patients

• Best results for tumors <3 cm

• Multiple techniques with complementary strengths

• Ongoing advances improving outcomes

Thank you.

--- Speaker Notes: To conclude, thermal ablation is a safe and effective option for carefully selected patients. Smaller tumors have the best outcomes, and emerging technical innovations continue to expand the field.

Closing message: Thank you.

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