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British Journal of Radiology (2003) 76, 742-745
© 2003 British Institute of Radiology
doi: 10.1259/bjr/35823935
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Percutaneous pulmonary radiofrequency ablation: difficulty achieving complete ablations in big lung lesions

K Steinke, MD 1 D Glenn, MBBS, FRANCZR 2 J King, MPH 1 and D L Morris, MD, PhD 1

Departments of 1 Surgery and 2 Radiology, University of New South Wales, The St George Hospital, Sydney, 2217 NSW, Australia

Correspondence: David L Morris, Professor of Surgery


   Abstract
Top
 Abstract
Introduction
 Material and methods
 Results
 Discussion
 References
 
The size of both primary and metastatic lung tumours often exceeds 3 cm in diameter at the time of diagnosis. The radiofrequency (RF) electrodes of the three leading companies currently in use are designed for a maximum ablation diameter of 5 cm. Therefore, the tumour to be ablated should not exceed 3 cm in maximum diameter, as a 1 cm safety ablation margin surrounding the tumour should ideally be achieved. A possible solution in treating larger tumours is to create overlapping ablations, a method successfully used in the radiofrequency ablation (RFA) of liver tumours. We report on the percutaneous overlapping ablation of three large lung metastases, 4 cm, 4.5 cm and 5 cm in their longest diameter. The largest of them showed incomplete ablation with residual viable tumour tissue. The overlapping percutaneous RFA of large lung tumours is feasible although the bigger the lesion, the higher the risk of incomplete ablation appears compared with smaller tumours treated by a single ablation.


   Introduction
Top
 Abstract
 Introduction
Material and methods
 Results
 Discussion
 References
 
Radiofrequency ablation (RFA) is still a relatively new minimally invasive treatment for primary and secondary lung tumours. Technical limits for the treatment are currently undelineated, and clinicians performing RFA are testing existing parameters in order to treat more difficult tumours in terms of size and location [1].

With the available electrodes distributed by the three leading companies, it is possible to achieve an ablation of 5 cm maximum diameter. Ideally a 1 cm area of necrotic safety margin should surround the tumour, therefore the maximal tumour diameter should not exceed 3 cm. In liver, overlapping ablations of larger tumours have been performed to treat larger lesions [2–4].

Both primary and metastatic lung tumours, at diagnosis, often exceed the maximum 3 cm diameter size [5, 6], which is currently the upper limit for single RFA.

This report describes the CT-guided percutaneous ablation of three large metastases in two patients with different primary tumours.


   Material and methods
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 Abstract
 Introduction
 Material and methods
Results
 Discussion
 References
 
The first patient described is a 63-year-old woman presenting with memory loss. A mass in the frontal lobe of the right cerebral hemisphere was resected, and found to be a metastasis from amelanotic melanoma. The patient had no prior history of melanoma and the primary site of the melanoma remains unknown.

A staging CT of the chest, abdomen and pelvis revealed a single 4 cm lobulated mass lesion in the left lower lobe (Figure 1aGo), confirmed to be a melanoma metastasis on biopsy. No further abnormalities were noted. The patient was not considered a candidate for thoracic surgery, but was treated instead with chemotherapy (Temozolomide, Temodal®). The lung lesion increased in size over 6 months, to 4.5 cm in maximum diameter. The patient was referred for percutaneous RFA which was considered the best therapeutic option for local control of the tumour.



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  		Figure 1. 63-year-old woman with amelanotic melanoma. (a) CT scan of chest shows 4.5 cm pulmonary metastasis in the left lower lobe (LLL). (b) CT scan obtained during radiofrequency (RF) ablation shows superomedial position of the electrode within the mass. (c) CT scan obtained during RF ablation shows inferolateral position of the electrode within the mass, a small basal pleural effusion has developed. (d) CT scan obtained 1 month after RF ablation at level corresponding to (a) shows pulmonary metastasis of same size as before, but homogeneously hypodense.

 
The second patient is a 52-year-old man diagnosed with metastatic right-sided renal cell carcinoma with multiple bilateral lung and bone metastases. He had palliative nephrectomy of his 17 x 15 cm diameter renal mass (pT3a, N0, M1 poorly differentiated clear cell renal cell carcinoma with sarcomatous areas), and was treated with interferon-alpha, interleukin-2 and 5-fluorouracil. After initial response to chemotherapy, follow up CT demonstrated enlargement of two metastases. A metastasis in the right upper lobe measured 4 cm in its largest diameter (not shown), and a metastasis in the left upper lobe measured 5 cm in its largest diameter (Figure 2aGo). His otherwise stable disease status contributed to the decision to percutaneously RF-ablate the two metastases. In the 5 weeks between the CT scan and the RF treatment both lesions have further increased in size, the one in the left lung (Figure 2aGo) becoming more lobulated.



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  		Figure 2. 52-year-old man with metastatic renal cell carcinoma. (a) CT scan of chest shows 5 cm pulmonary metastasis in the left upper lobe (LUL). (b) CT scan obtained during radiofrequency (RF) ablation shows dorsosuperior position of the electrode within the mass. (c) CT scan obtained during RF ablation shows anterosuperior position of the electrode within the mass. (d) CT scan obtained during RF ablation shows inferior position of the electrode within the mass. (e) CT scan obtained 1 month after RF ablation showing surrounding contrast enhancing rim (white arrows).

 
Both patients were treated under fluoroscopic CT-guidance with a 10 cm long expandable 15-gauge StarBurst XL RF electrode (RITA Medical Systems, Mountain View, CA), with creation of overlapping ablations. The 4 cm lesion (Patient 1, Figure 1b, cGo), and the 4.5 cm lesions (Patient 2, not shown) each had two overlapping ablations. The largest lesion, which measured 5 cm (Patient 2) was treated with three overlapping ablations (Figure 2b–dGo).

The generator was Model 1500 (RITA Medical Systems, Mountain View, CA), with a frequency of 460 kHz and power range of 0–150 watts. An ablation algorithm with staged deployment was applied with the lesions ablated for 20 min at maximum deployment and target temperature of 90°C. Upon completion of the ablations, the needle was heated on withdrawal to minimize the risk of seeding (track ablation).

Local anaesthesia was given with intradermal and subcutaneous 1%-lidocaine and both patients were consciously sedated with intravenous midazolam and pethidine (both: David Bull Laboratories, Victoria, Australia). Both patients had a post procedural chest radiograph (CXR) to assess the presence of pneumothorax, followed by another CXR prior to discharge. 1 month follow-up chest CT scans were performed.

The study had hospital Ethics Committee approval and signed informed consent was obtained for all patients.

Both patients reported in this paper have been treated off study, as they did not meet the study inclusion criteria of 3 cm maximum lesion diameter.


   Results
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 Abstract
 Introduction
 Material and methods
 Results
Discussion
 References
 
Neither patient had a pneumothorax demonstrated.

Both patients reported pleuritic pain, which required non-opioid analgesia and both developed small pleural effusions, which had resolved completely at 1 month CT follow-up scan. No further complications were noted. Both patients had low-grade fever (<38°C) for a few days post intervention.

At 1 month CT scan two of the three lesions did not change in size (Patient 1; Patient 2, lesion 1), while one lesion (Patient 2, lesion 2) had increased (Figure 2eGo). The two unchanged lesions, showing contrast enhancement on the pre-procedure CT-scans, were homogeneously hypodense at 1 month, possibly indicating necrosis (Figure 1dGo) and the largest lesion showed a peripheral enhancing rim, indicating residual viable tissue (Figure 2eGo).


   Discussion
Top
 Abstract
 Introduction
 Material and methods
 Results
 Discussion
References
 
Percutaneous RF tumour ablation is now a well-established treatment of primary and secondary liver tumours [2], but there is less experience in treatment of lung tumours. Pulmonary metastases can arise from most primary cancers and have been found at autopsy in 25–30% of all patients with malignant disease [7].

Tumours exhibiting preferential spread to the lungs as the only site of metastasis include sarcoma, renal cell cancer and head and neck cancer and tumours such as breast, melanoma and colorectal carcinoma typically metastasise to multiple organ sites [8].

Several studies on metastasectomies have recently been published in different cancer patient populations [9–11] demonstrating that metastasectomy is safe and provides extended survival.

Completeness of tumour resection was of prognostic significance with respect to survival in all analyses. Less agreement was found for disease-free interval (DFI), tumour type, number and size of metastases.

Both the patients detailed in this case report were judged to be ineligible for surgery because they had either a metastasising primary of unknown origin (Patient 1) or the patient refused to have bilateral surgery (Patient 2).

Percutaneous CT-guided RFA has recently been put forward as a minimally invasive treatment suitable for thoracic malignancies [1]. The aim of this treatment is to achieve local tumour control without the additional possible complications of surgery, and RFA can be performed on an outpatient or overnight stay basis.

The presently available and approved RF electrodes can create a maximum ablation diameter of 5 cm. There should be a 1 cm safety ablation margin surrounding the tumour and realistically it is only possible to treat a spherical lesion less than 3 cm diameter with a single ablation. Similar to RFA in liver, where large tumours are treated with overlapping ablations [2, 4] the same technique can be used for lung.

Exact probe placement into the tumour is crucial for successful ablations. Ideally, tumours measuring 3–5 cm in diameter should be treated with 6 overlapping ablations, 4 in the axial plane and 2 along the y-axis, with all ablations positioned to touch the centre of the tumour [12]. The lesion, part of a breathing patient, is a moving target. The extent of the ablation is limited by having large vessels adjacent to the tumours, which prevent a complete ablation because of the so called "heat sink-effect", which is caused by the circulating blood [13]. Therefore this can make it even more difficult to encompass large tumours.

We have now treated 5 lesions in 4 patients with overlapping ablations, and we have encountered a similar complication rate to that when treating single ablations, i.e. <3% [14]. Problems with tumour recurrence are the same as in liver, with incomplete ablation of the tumour border causing recurrence to occur at the periphery of the necrosis [2].

The advantage of RFA is that it can be repeated with multiple repeat ablations to destroy residual tumour. Furthermore RFA, even if it achieves lass than 100% tumour necrosis, may prove complementary to chemotherapy and radiation therapy in the treatment of lung tumours.

The development and improvement of monopolar and multiarray RF electrodes may allow for more successful treatment of larger tumours.

Received for publication January 6, 2003. Revision received May 20, 2003. Accepted for publication June 11, 2003.


   References
Top
 Abstract
 Introduction
 Material and methods
 Results
 Discussion
 References
 

  1. Dupuy DE, Mayo-Smith WW, Abbott GF, DiPetrillo T. Clinical applications of radio-frequency tumour ablation in the thorax. Radiographics 2002;22:259–9.
  2. Curley SA. Radiofrequency ablation of malignant liver tumours. Oncologist 2001;6:14–23.[Abstract/Free Full Text]
  3. Ruers T, Bleichrodt RP. Treatment of liver metastases, an update on the possibilities and results. Eur J Cancer 2002;38:1023–33.
  4. Livraghi T, Goldberg SN, Lazzaroni S, Meloni F, Ierace T, Solbiati L, et al. Hepatocellular carcinoma: radio-frequency ablation of medium and large lesions. Radiology 2000;214:761–8.[Abstract/Free Full Text]
  5. Pastorino U. Lung cancer: diagnosis and surgery. Eur J Cancer 2001;37:75–90.[CrossRef]
  6. Ike H, Shimada H, Ohki S, Togo S, Yamaguchi S, Ichikawa Y. Results of aggressive resection of lung metastases from colorectal carcinoma detected by intensive follow-up. Dis Colon Rectum 2002;45:468–73.[CrossRef][Medline]
  7. Ollila DW, Morton DL. Surgical resection as the treatment of choice for melanoma metastatic to the lung. Chest Surg Clin N Am 1998;8:183–96.[Medline]
  8. Davidson RS, Nwogu CE, Brentjens MJ, Anderson TM. The surgical management of pulmonary metastasis: current concepts. Surg Oncol 2001;10:35–42.[CrossRef][Medline]
  9. Pastorino U. History of the surgical management of pulmonary metastases and development of the International Registry. Semin Thorac Cardiovasc Surg 2002;14:18–28.[CrossRef][Medline]
  10. Friedel G, Pastorino U, Ginsberg RJ, Goldstraw P, Johnston M, Pass H, et al. Results of lung metastasectomy from breast cancer: prognostic criteria on the basis of 467 cases of the International Registry of Lung Metastases. Eur J Cardiothorac Surg 2002;22:335–44.[Abstract/Free Full Text]
  11. Pfannschmidt J, Hoffmann H, Muley T, Krysa S, Trainer C, Dienemann H. Prognostic factors for survival after pulmonary resection of metastatic renal cell carcinoma. Ann Thorac Surg 2002;74:1653–7.[Abstract/Free Full Text]
  12. Dodd GD 3rd, Soulen MC, Kane RA, Livraghi T, Lees WR, Yamashita Y, et al. Minimally invasive treatment of malignant hepatic tumours: at the threshold of a major breakthrough. Radiographics 2000;20:9–27.[Abstract/Free Full Text]
  13. Lu DS, Raman SS, Vodopich DJ, Wang M, Sayre J, Lassman C. Effect of vessel size on creation of hepatic radiofrequency lesions in pigs: assessment of the "heat sink" effect. AJR Am J Roentgenol 2002;178:47–51.[Abstract/Free Full Text]
  14. Wood BJ, Ramkaransingh JR, Fojo T, Walther MM, Libutti SK. Percutaneous tumour ablation with radiofrequency. Cancer 2002;94:443–51.[CrossRef][Medline]



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This Article
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Right arrow Articles by Steinke, K
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