Cryoablation May Offer Option for Metastatic Lung Tumors

David A. Woodrum, MD, PhD

The results of the first prospective multicenter trial of cryoablation in lung cancer show that this emerging treatment may be a safe, effective, and minimally invasive method of helping a specific group of patients with advanced disease.

At the Society of Interventional Radiology’s 38th Annual Scientific Meeting in New Orleans, David A. Woodrum, MD, PhD, an assistant professor of Radiology at the Mayo Clinic in Minnesota and one of the authors of the study,¹ presented the results and explained why this method of treatment appears promising.

Cryoablation is a process by which guided needles called cryoprobes are placed in the tumor and then cooled to temperatures as low as minus 100 degrees Celsius (Figure 1). Woodrum said that pieces of tissue die when frozen, forming the rationale behind exposing tumor tissue to extremely cold temperatures. This targeted treatment allows nearby healthy tissue to be spared.

Figure 1. Lung Cryoablation¹

This slide illustrates three important steps in the cryoablation process: identification of the tumor site, placement of the cryoprobes, and then freezing the tumor.

“In lung cancer, we have been searching for the right modality to treat limited metastatic disease, and a number of modalities have been tried, including radiofrequency ablation, microwave, and cryoablation,” Woodrum said. “The main advantage of cryoablation is that we can achieve a large zone of ablated or dead cells and we can actually see the edge of the ablation zone. We can monitor the growth of the ice as it grows to encompass the tumor and then grows to give us a margin around the tumor.”

Woodrum explained that a computed tomography (CT) scan can be used to monitor the growth of the iceball that forms around the tumor to make sure that it completely covers the tumor, which provides a significant advantage over other ablation methods where it may be difficult to monitor the ablation zone.

He said that a total of 40 patients were enrolled in the Evaluating Cryoablation of Metastatic Lung/ Pleura Tumors in Patients—Safety and Efficacy (ECLIPSE) trial. The participants had tumors that had metastasized to the lungs, with colon cancer (40%) and renal carcinoma (23%) as the two most common cancer diagnoses.

Among these patients, a total of 62 tumors were treated during the course of 48 procedures. Patients had up to three unilateral metastases or a maximum of five bilateral metastases, with each lesion measuring no more than 3.5 cm in size.

“If the tumors are greater than 3.5 cm in size, then the cryoablation is going to be more difficult just because of the volume that you have to cover,” said Woodrum, explaining that previous studies of cryoablation in other tumor types have helped determine the upper limit of the size of a tumor that could be treated with this technique.

Study participants underwent CT-guided cryoablation. Follow-up included CT imaging that was assessed at one week, three months, and six months. The primary endpoint of the study was to assess local tumor control.

Among the 40 patients enrolled in the trial, the median tumor size was 1.4 cm (range, 0.3-3.2 cm), and 80% of patients had unilateral disease while the remaining 20% of patients had bilateral disease.

Figure 2. ECLIPSE Trial Response Rates¹

The response rates capture the effectiveness of cryoablation as measured by the tumors killed or still dead at follow-up intervals.

The study found that the overall response rate was 100% at three months and 95% at six months (Figure 2). One patient did experience local failure. Adverse events were considered manageable, with 96% of reported adverse events being classified as grade 1 or grade 2.

Woodrum explained that despite the very cold temperatures of the needles being inserted into the tumors, the procedure itself is relatively painless. Most of the patients in the trial were under general anesthesia when they received cryoablation, although it may also be performed with conscious sedation. Woodrum said that some patients have reported soreness in their chest after the procedure is over, since the needles are being inserted in between ribs to reach the lung.

“This technology is offering another viable option for patients with pulmonary metastatic disease who are running out of options or have limited options,” Woodrum said. “The nice thing about this is that we treat the patients one day, they spend a night in the hospital, and, for the most part, the patients are going home the next day. So this is an advantage from the patient’s side as they see it, since there’s less time out of their lives for this treatment, and they can get on with their lives as well.”

Patients in this study will be followed for 60 months, according to Woodrum. Galil Medical, a device company that specializes in cryoablation, sponsored this study. According to Galil, a larger, multicenter trial involving a similar patient population is expected to launch sometime later in 2013.

REFERENCE 1. de Baere T, Farouil G, Woodrum DA, et al. Evaluatiing cryoablation of metastatic lung/pleura tumors in patients — safety and efficacy (ECLIPSE), preliminary safety outcomes. Presented at: Society of Interventional Radiology’s 38th Annual Scientific Meeting; April 13–18, 2013; New Orleans, LA. Abstract 33.