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Radiofrequency ablation of lung tumours |
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Riccardo Lencioni
University of Pisa, Pisa, Italy
Address for correspondence:
Università di Pisa, Dipartimento di Oncologia,
dei Trapianti e delle Nuove Tecnologie
in Medicina, Divisione di Radiologia
Diagnostica e Interventistica, Via Roma,
67 – 56126 Pisa, Italy
Tel: +39 (050) 992509
Email: lencioni@do.med.unipi.it
Introduction
Image-guided percutaneous radiofrequency (RF) ablation
is a minimally invasive technique for the treatment of
solid tumours that has been introduced into clinical
practice relatively recently. It is now considered a
feasible treatment option for patients with primary
hepatocellular cancer or limited liver metastases.
As the technology evolves, RF ablation is now being
evaluated in other types of tumours. A general review
of RF ablation was included in a previous issue of C2I2.
This paper focuses on the use of the technique for lung
tumours and updates an earlier review1 with new clinical
trial results presented at the Annual Scientific Meeting
of the Cardiovascular and Interventional Radiology
Society of Europe (CIRSE) in September 2005.
The lung is the most common site for primary cancer
worldwide (accounting for 13% of all new cancer cases
in the US), and is also a common site for metastatic
disease. Many of these patients are not suitable for
surgical treatment, often because of their age, poor
cardiovascular or respiratory function, or other serious
coexisting health conditions or because of the size and
location of the tumour. Hence, it is logical to extend the
use of RF ablation to patients with limited lung tumours
not eligible for surgical resection.
RF ablation
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| Figure 1. CT-guided ablation of lung tumour. Axial CT scan shows the
multi-tined electrode for radiofrequency ablation precisely placed into the
tumour (a). Multiplanar CT reformations confirm proper placement (b)
and indicate the degree of deployment needed to completely cover the
tumour (c). |
The principle of RF ablation is that the high-frequency
current from the RF generator passes between the
needle electrode placed in the tumour and a large
electrode on the patient’s skin. The alternating electric
field that is created between the electrodes induces
marked agitation of the ions resulting in frictional
heating of the surrounding tissue, which causes
irreversible damage. In animal studies, a well-defined
area of coagulation necrosis is observed 72 hours after
RF ablation, surrounded by a zone of hyperaemia that
gradually resolves. The technique may be particularly
suitable for lung tumours because the air in the
surrounding alveoli acts as insulation, helping to concentrate the energy in the lesion. However, since
each tumour or metastasis must be treated individually,
the technique is only suitable for patients with a small
number of lung lesions.
A careful pretreatment assessment is essential, including
chest CT to determine the exact size and position
of target tumours. During the procedure, the needle
electrode is positioned in the tumour, using the same
guidelines as for CT-guided lung biopsy, with the skin
entry site selected to allow the shortest and most
vertical path for the needle, avoiding blood vessels,
interlobar fissures and bullae. It is particularly important
to ensure the correct placement of the electrode needle
within the tumour, using image reconstructions in
multiple planes. At our centre, we use an expandable
electrode needle with 9 flexible hooks deployed from
the trocar tip (Figure 1); others use cooled tip electrodes.
The power output of the RF generator and duration
of ablation are programmed according to the tumour
volume and monitored by computer. A track ablation procedure is carried out at the end of the procedure
to reduce the risk of seeding of tumour cells. Lung RF
ablation is a painful procedure which requires adequate
pain relief. In our centre, we use conscious sedation with
a hypnotic and a short-acting analgesic. Other centres
carry out the procedure under a general anaesthetic,
although there may be a greater risk of pneumothorax
in the ventilated patient.
Clinical experience
Initial studies have indicated that RF ablation is well
tolerated by most patients and that it can achieve
complete necrosis of the targeted lesion (Figure 2).
Pneumothorax is the most common treatment-related
complication, typically occurring in up to 40% of cases,
with up to half of these requiring drainage.
We recently completed one of the largest trials of
RF ablation for lung tumours, with patients followed
for up to 27 months. The results of this prospective,
multicentre trial in patients with primary lung cancer
or lung metastases 3.5 cm or less in diameter who
were not candidates for surgery were presented at
CIRSE in Nice in September 2005. One hundred
and six patients (36 women and 70 men) with
186 malignant tumours were enrolled in this trial.
Thirty-three patients had non-small cell lung cancer,
53 had colorectal cancer metastases and 20 had
metastases from other primary malignancies; none
were suitable for surgery. Patients underwent RF ablation treatment with CT guidance and under
conscious sedation as described above. No procedurerelated
deaths occurred. There were 27 cases of
pneumothorax requiring treatment, 4 pleural effusions,
2 cases of pneumonia and one case of atelectasis.
At a CT evaluation 3 months after the procedure,
complete ablation of the tumour was observed in
173 of 186 tumours, a primary effectiveness rate
of 93%. Overall survival of the primary lung cancer
patients was 69% at 1 year and 49% at 2 years.
However, many of the deaths were not cancer related
and when these were excluded, the cancer-specific
survival rates were 91% at 1 and 2 years. In patients
with lung metastases from colorectal cancer, the
survival rates were 88% at 1 year and 72% at 2 years,
after exclusion of non-cancer-related deaths.
These results are encouraging and suggest that RF
ablation can improve survival, reduce pain, and improve
quality of life in patients with unresectable lung
tumours. However additional clinical trials are required
to further evaluate the place of RF ablation in the
management of primary tumours and metastases in the
lung, either alone or in conjunction with chemotherapy
or radiotherapy.
Further reading
1. Lencioni R, Crocetti L, Cioni R et al. Radiofrequency ablation of
lung malignancies: Where do we stand? Cardiovasc Intervent Radiol;
27: 581–90.
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| Figure 2. Lung tumour treated with radiofrequency ablation. Pre-treatment CT shows the focal mass (a). CT obtained after electrode placement confirms
proper deployment (b). CT after the ablation shows ground-glass density area encompassing the native tumour as well as a safety margin of surrounding
lung parenchyma (c). T1-weighted gadolinium-enhanced MR imaging confirms complete ablation by showing a non-enhancing hypointense area of
coagulation necrosis surrounded by a thin enhancing rim representing inflammatory reaction (d). |
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