90 tumours in 45 patients treated with radiofrequency ablation (RFA) between April 2009 and August 2013 during 83 separate procedures were analysed using a prospective database
All procedures were performed under deep conscious sedation (intravenous morphine and midazolam) using pulse oximetry and real time Bispectral Index (BIS) monitoring (Aspect Medical Systems,
Inc.
Norwood,
MA,
USA).
Patients were positioned depending upon the location of the lesion.
Local anaesthetic (20ml 1% lignocaine) was infiltrated to the pleura under CT guidance.
Ablation was performed using either the Boston Scientific LeVeen needle (Natuck,
MA,
USA) or the Covidien Cool-tip system (Mansfield,
MA,
USA).
Choice of equipment was based upon lesion size and location.
Various manipulations including introduction of a pneumothorax,
hydro-dissection with 5% dextrose solution and electrode angulation were used to achieve satisfactory access and a clear margin.
An ablation zone extending at least 5mm beyond the margin of the lesion,
as assessed by the extent of ground glass shadowing on an immediate post treatment CT,
was considered satisfactory.
If ablation was felt to be unsatisfactory or incomplete the needle was repositioned and the lesion retreated.
A chest X-ray was performed at 4 hours post procedure.
Follow up whole body CT imaging was performed at 1 month and then at 3 month intervals until three years and then 6 monthly until 5 years.
All CT was performed using a GE Lightspeed 64-slice CT (GE systems,
Milwaukee,
USA) with dynamic IV contrast enhancement (100mls iodinated contrast (300mg/ml) delivered via a peripheral or central IV line at 3-5ml/sec).
Local recurrence or progression was felt likely when the ablation zone showed an increase in size on the 4 month CT or later,
where there was typical enhancement related to the lesion or where there were other morphological changes suggesting regrowth.
The following data were recorded prospectively for each patient: histologically confirmed nature of the primary tumour,
site and number of metastases,
presence of metastases at other sites and if the patient received pre-treatment chemotherapy or other treatment e.g.
prior liver or lung resection (table 1).
On a lesion-by-lesion basis the following data were recorded: site and size of the lesion,
technical parameters of the ablation,
length of the lesional tumour progression free survival,
overall survival and significant complications.
These were defined as complications,
which resulted in the patient requiring further treatment or prolonged inpatient stay as a direct result of the RFA.
Small pneumothoraces noted on imaging following the procedure and which did not require intervention were not counted as significant.