Ablative Therapy for Lung Lesions
Ablative therapy stands at the forefront of innovative approaches in the management of lung lesions, offering a minimally invasive alternative to traditional surgical resection. This advanced technique involves the precise application of thermal energy or other specialized modalities to destroy or render non-functional targeted abnormal tissue within the lung. Through methods like Microwave Ablation (MWA), Radiofrequency Ablation (RFA), Cryoablation, and Irreversible Electroporation (IRE). The selection of the appropriate ablative modality, guided by factors such as lesion size, location, and patient characteristics, plays a pivotal role in optimizing outcomes.
Ablative Modalities for Lung Ablation:
| Modality | Advantages |
|---|---|
| Radiofrequency Ablation (RFA) | - Suitable for smaller tumors (<10mm) - Very susceptible organ (air in lung parenchyma act as insulator) |
| Microwave Ablation (MWA) | - Tumor diameter (>3 cm) and proximity to large vessels associated with higher incomplete treatment rate |
| Cryoablation (CA) | - Effective for tumors near pulmonary hilum or major vessels - Less pain to patients than RFA/MWA |
Patient Selection for Lung Ablation:
| Indication | Description |
|---|---|
| Stage Ia NSCLC | Contraindications for surgery or SRT Medically inoperable |
| Unresectable Local Recurrence | Recurrence after surgery or radiation therapy |
| Multiple/Synchronous NSCLC | Suitable for definitive ablative treatment |
| Association with TKI | Aiming to control residual tumor volume |
| Recurrence after Surgery/Radiation Therapy | Suitable for percutaneous ablation as rescue therapy |
| Metastasis from Various Cancers | Mainly colorectal, lung, renal, melanoma, hepatocellular carcinoma, sarcoma |
| Maximum of 4 lesions per lung | All with a maximum tumor diameter of <3.5 cm. Treat one lung at a time. |
Contraindications for Lung Ablation:
| Contraindication | Description |
|---|---|
| Severe lung emphysema with bullae | Risk of untreatable fistula and respiratory failure |
| Life expectancy < 3 months | Limited survival time |
| Eastern Cooperative Oncology Group (ECOG) > 2 | Poor general health status |
| Non-correctable hemorrhagic diathesis | Risk of uncontrollable bleeding during the procedure |
| Presence of small cell lung carcinoma | Different treatment approach needed for small cell lung cancer (not suitable for ablation) |
| Tumors located near large vessels or pulmonary hilum, pericardium (< 1 cm) | 1. High risk due to proximity to critical structures. 2. Cryoablation can be used for controlled ablation |
| Pacemaker | Ablations can be performed under cardiological supervision. |
CT Techniques for Lung Ablation:
| Modality | Parameters for Minimizing Radiation Dose |
|---|---|
| Conventional CT-guided Technique (CCT) | Adjust parameters for minimum radiation while maintaining sufficient quality for the procedure |
| CT-fluoroscopy-guided Technique (CTF) | Consider intermittent multislice fluoroscopy for reduced radiation exposure |
| Cone-beam CT-guided Technique (CBCT) | Utilize advanced needle planning and real-time guidance for reduced radiation exposure |
Radiological Findings at Different Phases:
| Phase | Findings | Description |
|---|---|---|
| After Treatment ( < 24 hours, CT) | Consolidation | Central consolidation with peripheral GGO > 5mm |
| Disease Progression | Irregular and peripheral nodular enhancement or within central consolidation | |
| Early-phase (24 h - 1 month, CT/PET-CT) | Ground-glass opacity | Gradually resolves, replaced by thin consolidation zone separating central from adjacent lung. |
| Consolidation (1 month) | Extensive, larger than original tumor. | |
| Disease Progression | Irregular and peripheral enhancement or within central consolidation | |
| Intermediate-phase (1 - 3 months, CT/PET-CT) | Enhancement | Less than original tumor, benign periablational enhancement for up to 6 months. |
| Cavitation (in large lesions) | Secondary to drainage of necrotic tissue by adjacent bronchi. | |
| Pleural thickening | Transient increase in hilar and mediastinal lymph nodes. | |
| FDG Uptake Patterns (PET-CT) | Response patterns: diffuse, peripheral, heterogeneous, peripheral plus focal. | |
| Progression/recurrence patterns: - Solitary focal or diffuse peripheral with focal uptake. - Any hypermetabolic activity after 2 months within ablation site. |
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| Late-phase (> 3 months, CT/PET-CT) | Stability and Size Reduction | Stable for 3-6 months, then progressively decreases to smaller than original tumor. |
| Morphology | Varies between ovoid, rounded, linear, eventually forming a lung scar. | |
| Patterns (Post-ablation) | Fibrosis (most common), Nodular pattern, Cavitation, Atelectasis, and Local tumor progression. |
Clinical Outcomes:
| Indication | Treatment Method | Survival Rates (1, 2, 3, 4, 5 years) | Local Recurrence Rates (1, 2, 3 years) |
|---|---|---|---|
| Stage I NSCLC | RFA | 78%, 57%, 36%, 27%, 27% | 12%, 18%, 21% |
| MWA | 78-89%, 54-63%, 39-43%, 16% | - | |
| CA | 67.8% (5-year) | 36.2% | |
| Alternative Indications | After Radiotherapy + Chemo | 35 months (OS) | - |
| With Immunotherapy + CA | Survival increase (compared to CA alone) | - | |
| Oligometastatic Lung Disease | RFA | 62 months (OS), 5-year OS: 52% | 5.9%, 8.5%, 10.2%, 11.0% |
| MWA | 91.3% (1-year OS), 75% (2-year OS) | - | |
| CA | Response rate without local recurrence: 85.1% (12 months), 77.2% (24 months) | - |
Complications related to Lung ablation:
| Complications | Incidence | Notes |
|---|---|---|
| Pneumothorax | Up to 50% during procedure (5–10% requiring chest drain) | - Pre-existing emphysema increases risk. - Careful introduction of air as thermal buffer. |
| Pleural Fluid | Aseptic pleuritis: 2.3% | - Risk factors: Number of pleural punctures, previous systemic chemotherapy |
| Pulmonary Abscess | Incidence: 1.6% | - More common in pre-existing inflammatory lung disease. |
| Vascular Complications | - Pulmonary Haemorrhage: 7–8% - Pseudoaneurysm: 0.2% | - Risk factors: Tumour size, platelet count, proximity to large vessels |
| Lung Inflammation | Incidence: 0.6% | - Greater risk with tumours ≥2 cm, and prior radiotherapy |
| Thoracic Wall Injury | Rib fractures reported up to 13.5% | Risk increases with proximity to pleura, major nerves, or previous thoracic surgery |
| Tumour Recurrence | Local recurrence reported up to 32% | - Risk factors: Tumour size, stage, proximity to vessels |
| Needle Tract Seeding | Incidence: 0.2% | - Care needed when manipulating needle to prevent withdrawal through tumour. |