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J Thorac Cardiovasc Surg 2006;131:1007-1013
© 2006 The American Association for Thoracic Surgery
General Thoracic Surgery |
a Division of General Thoracic Surgery, School of Medicine, Keio University, Tokyo, Japan
b Division of Diagnostic Radiology, School of Medicine, Keio University, Tokyo, Japan
Received for publication October 8, 2005; revisions received December 8, 2005; accepted for publication December 22, 2005. * Address for reprints: Masafumi Kawamura, MD, Division of General Thoracic Surgery, School of Medicine, Keio University, 35 Shinanomachi, Shinjuku-ku, Tokyo 160-8582, Japan (Email: kawamura{at}sc.itc.keio.ac.jp).
| Abstract |
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METHODS: The procedure was performed after achievement of local anesthesia for 35 tumors in 20 patients (12 male and 8 female patients; mean age, 57 years). The primary end point was the safety and feasibility of cryoablation, and the secondary end point was tumor control assessed by follow-up dynamic computed tomographic scanning performed every 3 months.
RESULTS: Of the 22 sessions of cryoablation, pneumothorax occurred in 11, hemoptysis occurred in 8, and there was 1 case of phrenic nerve palsy. The mean hospital stay was 2.6 days. There was local recurrence of 7 (20%) tumors in 7 (35%) patients during a 9- to 28-month (median, 21 months) follow-up period. One-year survival according to the Kaplan-Meier method was 89.4%.
CONCLUSION: Percutaneous cryoablation therapy for metastatic lung tumors is feasible and minimally invasive, with satisfactory local control.
| Introduction |
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Cryoablation is used to treat hepatocellular carcinoma
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or prostate carcinoma,
2
but although Wang and associates
3
have reported their experience of more than 200 cases of percutaneous pulmonary cryoablation during local anesthesia without major complications, the feasibility and efficacy of this technique for lung tumors have not been established.
Experiments in pigs have shown that a 2- or 3-mm-diameter cryoablation probe can freeze an area (known as an "ice ball") 2 to 3 cm in diameter and 4 cm in length after 2 cycles of freezing and thawing.
4
Furthermore, a technique of puncturing the center of small intrapulmonary nodules under computed tomographic (CT) fluoroscopic guidance has been developed from the experience of CT-guided lung biopsy.
The surgical approach for small pulmonary metastases is usually a wedge (or incomplete) resection, which is considered sufficient for local curability. Good results after complete resection of isolated pulmonary metastases from extrathoracic malignancies have been reported,
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although others report that the extent of resection does not affect the prognosis.
6
However, because patients with metastatic pulmonary tumors are likely to develop new lesions after treatment, the loss of pulmonary function associated with therapy should be minimal.
Therefore we considered that percutaneous cryoablation under CT guidance with local anesthesia as a locally curative treatment for small lung tumors (<3 cm in diameter) should be possible and feasible. Our prospective study was approved by the institute's ethical review board.
| Methods |
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The characteristics of the patients and the main reasons for the choice of cryoablation as an alternative to surgical resection are shown in Table 1.
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It takes 20 to 30 minutes to place a guide needle into the optimal position in the targeted tumor, and cryoablation is not performed until all gauge needles are inserted.
Evaluation and Statistical Analysis
The primary end point of this study was the early outcome and feasibility of using cryoablation for pulmonary metastatic tumors smaller than 3 cm. The secondary end point was the effect of cryoablation on radiographically determined tumor control. We also evaluated the type and frequency of complications, radiographic evidence of tumor response after cryoablation treatment, and overall survival.
Patients underwent a preoperative chest CT scan and a repeat scan on the day after the cryoablation procedure. Follow-up dynamic CT chest scans of patients without iodine allergy were carried out at 1-month and then 3-month intervals. Increase of the treated lesion size on follow-up CT scan was diagnosed as local recurrence. In some cases CT-guided needle biopsy was added to obtain a definite diagnosis. Changes in tumor mass after cryoablation were measured according to the Response Evaluation Criteria in Solid Tumors (RECIST) protocol,
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which is based on objective measurements of lesion size before and after treatment. Complete response means lesion disappearance (scar) or less than 25% of original size. Partial response (PR) means a greater than 30% decrease in the sum of the largest diameter of all targeted lesions. Stable disease (SD) means a less than 30% decrease in the sum of the largest diameter of all targeted lesions. Progressive disease (PD) means an increase of greater than 20% in the sum of the largest diameter of all targeted lesions. Change in each tumor size is also important for evaluating the efficacy of cryoablation because patients with metastatic lung tumors usually have multiple metastatic lesions. Therefore change in each tumor was evaluated with the same protocol as RECIST. Because cryoablation can cause scar formation during the healing process, the lesion size after treatment alone does not necessarily reflect treatment efficacy. Therefore in addition to RECIST, clinical outcome according to the follow-up CT scan after more than 1 year can be noted.
The Kaplan-Meier method was used to analyze cumulative survival after the initial cryoablation.
| Results |
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The main reasons why those patients underwent cryoablation instead of surgical intervention were refusal of surgical intervention in 6 patients, inadequate predicted postoperative pulmonary reserve in 5 patients, extrapulmonary metastases in 8 patients, and asthma in 1 patient (Table 1).
Pneumothorax occurred in 11 of the 22 sessions, primarily after the completion of the ablation procedure. A chest tube was inserted in 1 case, transient needle aspiration was performed in 3 cases, and in 7 cases no additional treatment was given. In 7 cases a small amount of pleural effusion was detected on a chest CT scan carried out on postoperative day 1, but no additional treatment was required. Pleural dissemination was detected during the follow-up period in 1 patient whose postoperative CT scans did not show any pleural effusion. Because there had been multiple pulmonary metastases on the lung surface, it is unclear whether the cryoablation induced pleural dissemination. Hemoptysis occurred during 8 sessions and subsided in a few days in all patients. There was no apparent correlation between tumor location and the incidence of hemoptysis. Phrenic nerve palsy occurred during 1 session for a tumor located near the left phrenic nerve and had not improved when the patient died of brain metastases 9 months later (Table 2).
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The response to cryoablation according to RECIST was complete response in 2 patients, PR in 8 patients, SD in 8 patients, and PD in 2 patients, giving a response rate of 50%. In 3 of 8 patients with PR and 2 of 8 patients with SD, there was tumor recurrence. The response of each tumor was complete in 8 patients, partial in 11 patients, SD in 14 patients, and PD in 2 patients, giving a response rate of 54.3%.
One patient died of brain metastases 9 months after cryoablation, and another patient died of bone and kidney metastases 10 months later, but neither had pulmonary local recurrence. The remaining 18 patients survived more than 1 year. The follow-up period was 9 to 28 months (median, 21 months), and in the 9 to 12 months after cryoablation, there was local recurrence of 7 (20%) tumors (median time to progression of 9 months) in 7 (35%) patients: 5 patients underwent repeat cryoablation without complications, 1 patients initially refused surgical intervention and underwent surgical resection, and 1 patients was given chemotherapy for both the recurrent and new lesions. There was 1 case of suspected subcutaneous recurrence along the insertion track, which was surgically resected. To date, there have been no cases of local recurrence after repeat cryoablation (Table 3).
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| Discussion |
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One patient required a chest tube for pneumothorax, but for the other 10 cases of a small amount of air leakage, transient manual aspiration was sufficient to control it. Hemothorax requiring chest tube drainage did not occur. Izumi and coworkers
9
observed from animal experiments that the coagulated blood surrounding the outer sheath apparently prevents massive air leakage and bleeding in the damaged pulmonary tract. The patient with the chest tube remained in the hospital for 9 days after treatment, but the average hospital stay was 2.6 days, which is shorter than the 4.5 days after video-assisted wedge resection at the same hospital.
As for other complications, hemoptysis occurred in 50% of sessions. In animal experiments rupture of the capillary wall and hemorrhage in the alveolar space were observed microscopically in the frozen area after thawing.
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We suppose this phenomenon is a kind of hemorrhagic pulmonary edema caused by the death of endothelial cells. Therefore hemoptysis seems inevitable after pulmonary cryoablation and is not a serious condition because it is caused by the rupture of capillaries rather than large vessels. Actually, hemoptysis was not usually associated with shortness of breath.
There are some reports on the use of radiofrequency ablation (RFA) for pulmonary malignancies.
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The RFA devices are more compact and cheaper than those for cryoablation. It was reported that in RFA 1 retreated patient with metastatic disease died of massive hemoptysis 21 days after open RFA of a central nodule.
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Because the patient had also undergone brachytherapy 4 days prior, the cause of the fistula between the bronchus and the large pulmonary vessel was unclear; however, the authors state that they have ceased using RFA for central nodules since that complication.
We used cryoablation for centrally located tumors in 3 cases without any major complications (Figure 4), although the number of patients in this study is small. We know that the bronchial wall can resist temperatures of 120°C to 130°C because tracheas obtained from cadavers for transplantation can be deep-frozen.
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Some reports suggest that the collagenous architecture of the central bronchi and vasculature is preserved by endobronchial cryotherapy.
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On the other hand, the wall of large blood vessels heated by circulating blood during cryoablation seems to preserve the vessel wall structure.
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For tumors larger than 2.0 cm in diameter, 2 or more cryoprobes are usually inserted around the tumor, but in those cases, the ice ball is irregular in shape, and it is difficult to accurately assess the positional relationship of the tumor and ice ball on CT images, although 3-dimensional CT should help. However, more basic research is required, and we do not use cryoablation for tumors larger than 3.0 cm in diameter. Nevertheless, there was local recurrence of approximately 20% of the ablated tumors and further improvements in the technique, and the CT images are necessary to decrease this rate. Of course, another cause of local recurrence after cryoablation is that the metastatic tumor might have satellite lesions or there is microinvasion into the lymph ducts, and local treatment, such as cryoablation or wedge resection, has the limitation to curative local control of metastatic lung tumors.
The response of the tumors was evaluated according to RECIST, and even though the marked scar formation around the tumor after cryoablation would seem to make accurate evaluation of tumor size on CT images impossible, of the 11 of 14 tumors diagnosed as SD by RECIST, local recurrence has not occurred during follow-up of more than 14 months. Long-term follow-up with CT scanning periodically is thought to be the most appropriate way to evaluate local control of tumors after cryoablation. Positron emission tomography might also be very useful to evaluate local control, although we have not done this in the present study. Because all cases of recurrence occurred 6 to 12 months (median, 9 months) after cryoablation, particular attention must be given to this period, especially for the common metastatic lung tumors, although longer observation of low-grade malignant tumor is necessary. A larger multi-institutional study would be ideal to further evaluate feasibility, but we need to collect more data before such studies can be designed. We also need to train individuals to gain better recognition of this technique. At our institution, we start by training the techniques necessary for CT-guided biopsy.
| Conclusion |
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| References |
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