Pulmonary Parenchymal Changes in Image-Guided Ablation Cases for Nonsurgical Lung Cancer Patients

ABSTRACT: The high rate of recurrence in lung cancer patients who have undergone metastatectomy indicates a suitable patient population for image-guided ablative techniques. Additionally, patients with solid lung neoplasms that are medically inoperable are often candidates for ablative procedures such as radiofrequency ablation, microwave ablation, cryoablation, and stereotactive beam radiation. We present a series of representative cases and review the utility of these four ablation techniques.

IO Learning: 2020;8:E25-E28. Epub 2020 March 16.

Key words: cryoablation, microwave ablation, radiofrequency ablation, stereotactive beam radiation

BACKGROUND

Patients with lung cancer who have undergone metastatectomy have a 10-year survival rate of approximately 25% after surgical resection. The high rate of recurrence in this group indicates a suitable patient population for image-guided ablative techniques. Additionally, patients with solid lung neoplasms that are medically inoperable are often candidates for ablative procedures such as radiofrequency ablation, microwave ablation, cryoablation, or stereotactive beam radiation. Post-treatment changes after hepatic ablation are well studied, and similarly, with the ubiquity of computed tomography imaging, it is imperative to recognize the lung parenchymal evolution of treated lesions to differentiate normal postablative changes from recurrence.

CASE PRESENTATIONS

Case #1: Radiofrequency Ablation (RFA). A 70-year-old woman with metastatic non-small cell lung cancer (NSCLC) with history of left upper lobectomy presented for RFA  (Figure 1). 

Factors associated with decreased rate of recurrence after RFA include size and location of the neoplasm; specifically, size <3-3.5 cm, peripheral location, and location 3-10 mm away from a vessel (avoiding the heat sink effect). Intraprocedurally, a 1 cm margin ablation surrounding the neoplasm has been shown to reduce incomplete ablation, as 8 mm and 6 mm safety zones for adenocarcinoma and squamous cell carcinoma, respectively, have been shown to reduce recurrence. Post-RFA biopsy has been shown to be unreliable for histopathologic verification of complete tumor ablation due to sampling error and false-positive factors, such as ghost cell phenomenon, where acute postablation cells lack classic signs of coagulation necrosis.^1-3

Case #2: Microwave Ablation. A 62-year-old man with history of NSCLC with enlarging left upper lobe lung nodule concerning for adenocarcinoma underwent treatment with microwave ablation (Figure 2). 

Advantages of microwave ablation over RFA include achieving higher temperatures and shorter ablation times. Tumors <2 cm have greater likelihood of successful ablation with a single treatment. Factors that preclude microwave ablation include extensive metastatic disease, proximity to main airways or vasculature, and elevated international normalized ratio.^4-6

Case #3: Cryoablation. A 72-year-old man presented with metastatic colon adenocarcinoma with lung nodule and underwent treatment with cryoablation (Figure 3). 

Cryoablation has proved safe and effective for ablating and debulking tumors, providing radical cure or palliation. With cryoablation, increased cellular injury is observed with rapid freezing, lower temperatures, increased time at minimum temperatures, slow thawing, and repeated freeze-thaw cycles. When cryozones (pathology-proven areas of cell necrosis) and cryolesions (visual regions of destruction) are similar, triple-freeze protocols have been shown to induce greater necrosis, and thus, decreased risk of recurrence. Compared with other ablative techniques, cryoablation allows for good intraprocedural visualization under computed tomography guidance.^7-10

Case #4: Stereotactic Beam Radiation Therapy (SBRT). A 66-year-old woman with a history of NSCLC underwent treatment with SBRT (Figure 4). 

Indications for therapy with SBRT include treatment of early-stage node-negative NSCLC in medically inoperable patients, patients with local recurrence of NSCLC after definitive radiation or surgery, and patients with multiple synchronous, early-stage primary lung cancers. Palliative radiation therapy can be used to decrease the tumor or metastatic burden. SBRT offers accurate delivery of highly ablative radiation doses to a selected target with control of radiation dose delivery. Three-dimensional conformal radiation therapy allows for higher-dose delivery to tumor cells with greater exclusion of normal parenchyma. SBRT demonstrates high local control rates of ≥90% in the lung.^11-13

References

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7. Zhang YS, Niu LZ, Zhan K, et al. Percutaneous imaging-guided cryoablation for lung cancer. J Thorac Dis. 2016;8(Suppl 9):S705-S709. 

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From the Pennsylvania Hospital, University of Pennsylvania Health System, Philadelphia, Pennsylvania.

Disclosure: The authors have completed and returned the ICMJE Form for Disclosure of Potential Conflicts of Interest. The authors report no conflicts of interest regarding the content herein.

Address for Correspondence: Sean Maratto, MD. Email: Sean.Maratto@pennmedicine.upenn.edu