Thermal ablation of lung tumors

Abstract

The 5-year survival for all stages of nonsmall cell lung cancer (NSCLC) remains bleak, having increased from 13% to just 16% over the past 30 years. Despite promising results in nonoperative patients with NSCLC and pulmonary metastatic disease, thermal ablation appears to be limited by large tumor size and proximity to large vessels. This article discusses the particular challenges of performing thermal ablation in aerated lung tissue and reviews important considerations in performing ablation including treatment complications and imaging follow-up. The article compares and contrasts the three major thermal ablation modalities: radiofrequency ablation, microwave ablation, and cryoablation.

Fig. 1

55-year-old woman with history of metastatic colorectal cancer. History of previous liver ablation, now with a new left lower lobe pulmonary metastasis. (A) 9 mm left lower lobe colorectal metastasis (arrow). (B) A single Cool-tip electrode was positioned, but it was somewhat eccentric in the nodule and the ground glass opacity associated with the ra-diofrequency ablation only partially enveloped the nodule (arrow), suggesting that a complete treatment was not accomplished. (C) 6 months later, the nodule had increased in size, and it was determined that there was local tumor progression (arrow). (D) For the retreatment, a Cool-tip cluster electrode was used to increase the power deposition, and a better technical result was achieved. (E) However, the increased invasiveness resulted in a large hemothorax that required chest tube placement and prolongation of her hospitalization stay. (F) 2-year follow-up computed tomography scan shows a small residual scar (arrow), but no evidence of local tumor progression.

Fig. 2

A deployable array electrode positioned within a right lower lobe nonsmall cell lung cancer. Note that the increased surface area associated with this electrode allows greater power deposition, but decreased control and increased invasiveness. (Courtesy of Ricardo Lencioni, MD, Pisa, Italy.)

Fig. 3

51-year-old man with history of metastatic colorectal carcinoma s/p hepatic and pulmonary resection, including right pneumonectomy, referred for radiofrequency (RF) ablation of a single left lower lobe metastatis. (A) 1 cm peripheral pulmonary nodule in left lower lobe (arrow), with no large adjacent vessels. (B) A single Cool-tip electrode was placed centrally in the tumor for the ablation (arrow). (C) Immediately following RF ablation, there was ground glass opacity entirely encompassing the lesion (arrow), consistent with a technically successful ablation. Note the small pneumothorax that resolved without treatment. (D) 4-month follow-up computed tomography (CT) demonstrates cavitation of the nodule (arrow), a favorable prognostic sign. (E) 14-month follow-up positron emission tomography/CT scan demonstrates parenchymal scarring, but no significant radiotracer uptake, consistent with a successful ablation.

Fig. 4

80-year-old man with multiple comorbidities, including oxygen dependence with a cavitary squamous cell carcinoma in the left lower lobe. (A) 2 cm peripheral cavitary squamous cell carcinoma in the left lower lobe (arrow). (B) Two microwave antennae were positioned within the tumor with one seen on this imaging plane. Note the small pneumothorax (arrow), which was later treated with a small-bore chest tube. (C) Due to the cavitary nature of the tumor, saline was injected into the tumor to increase the water content and thus the likelihood of heating all of the tissue. Note that after this, the tumor no longer appears cavi-tary (arrow). (D) Immediately after the ablation, confluent ground glass opacity develops around the tumor (arrows), indicating a combination of ablation zone and parenchymal hemorrhage. (E) 6-month follow-up computed tomography scan demonstrates a residual nodule (arrow), but without cavitation, and the patient is now 18 months post-ablation with no evidence of disease. (Courtesy of Damian Dupuy, MD, Providence, Rhode Island.)

Fig. 5

Comparison of radiofrequency (RF) and microwave (MW) in a porcine lung model. (A) The MW ablation was associated with a more rapid and larger ablation zone than the RF ablation as shown by the development of ground glass opacity on the noncontrast computed tomography (CT) images obtained during the ablation. (B) The CT findings were confirmed on pathology also. (From Brace CL, Hinshaw JL, Laeseke PF, et al. Pulmonary thermal ablation: comparison of radiofrequency and microwave devices by using gross pathologic and CT findings in a swine model. Radiology 2009;251:705–11; with permission.)

Fig. 6

62-year-old woman with history of metastatic colorectal cancer. After treatment and resection, she had two residual pulmonary metastases and was referred for ablation. (A) 1.3 cm right middle lobe colorectal metastasis (arrow). (B) During pulmonary cryoablation, ground glass opacity develops in the lung parenchyma around the metastasis, and the higher attenuation ring (arrow) indicates the edge of the ice ball. One of three cryoprobes used for the ablation is visualized. (C) 1-month follow-up noncontrast computed tomography scan demonstrates expected enlargement of the apparent tumor size due to the ablation zone changes (arrow) and some central cavitation (arrowhead). (D) 4-month and (E) 12-month follow-up demonstrates progressive reduction in ablation zone size indicative of a successful ablation (arrows).

Fig. 7

73-year-old woman with history of severe emphysema and nonsmall cell lung carcinoma in the right upper lobe. She was medically inoperable and therefore, initially treated with radiotherapy and had a good response. (A) 2 years after radiotherapy, she developed positron emission tomography scan-confirmed recurrent disease (arrow) and was not able to receive any further radiation. Therefore, she was referred for ablation. (B) Cryoablation was performed with 4 cryoprobes. Note low attenuation within tumor, right up to the aorta and mediastinum (arrows). (C) After the ablation, the patient developed a large and growing pneumothorax that required chest tube placement (arrow) and significant intraparenchymal hemorrhage (arrowhead), both of which contributed to significant postablation respiratory compromise. (D) Pre-ablation chest radiograph showed normal relationship of the hemidiaphragms. (E) During the ablation, the right phrenic nerve was damaged, resulting in right hemidiaphragm paralysis, confirmed with a sniff test and seen as elevation of the right hemidiaphragm on postablation chest radiograph (arrow). These complications all resolved over time and in approximately 2 months, the patient returned to near her previous level of function.