- Patient selection:
All indications must be decided in dedicated multidisciplinary meeting.
A thermal adrenal ablation is recommended for patient with solitary adrenal metastasis or oligo metastatic disease usually defined as the existence of one to five isolated macro metastases6. The diameter of the metastasis must not exceed 5 cm (Fig 1).
- Cathecholamine release:
The risk of catecholamine release is important during the procedure7 and needs special care in order to avoid hypertensive injury.
Two risk factors of hypertensive crisis have been described by Fintelman et al8 :
*Size of the lesion > 4.5 cm
*Adrenal residual tissue on pre operative imaging
They proposed a pre-medication even if there is no official recommendations for this :
* Selective reversible alpha-1 receptor blocker doxazosin mesylate 1 mg by mouth once daily for 14 days before the procedure
* Long-acting selective beta-1 receptor blocker metoprolol succinate 25 mg by mouth once daily for 4 days before the procedure
Patients should have a medical consultation with informed anesthesiologist and cardiologic pre-operative screening.
During the procedure,
It is mandatory to work with informed anesthetist and to keep a good communication.
Furthermore,
it has been proposed to get an invasive blood pressure monitoring because hypertensive crisis can have a short duration and can be missed with classic blood pressure monitoring.
- Procedure details
*Needle approaches and patient positioning:
Prone position with posterior approach is the more usual way to treat adrenal metastases with or without transpleural puncture (Fig 2)
An ipsilateral side down positioning (Fig 3) can also be useful to avoid pleural damage.
Trans hepatic approach9 will be helpful when no direct approach is possible but bleeding risk will be increased.
*Imaging guidance:
- Adrenal thermal ablation is usually performed under CT scanner guidance with general anesthesia10.
- Some cases have been described in the literature with an ultrasound guidance but needle placement can be challenging11.
- Interventional MRI can be used laso especially in case of cryotherapy,
allowing better visualization of ice ball.
The major limitation of its use is the limited number of MRI dedicated to interventional radiology.
* Biopsy or not Biopsy?
Biopsy prior or during procedure is debated12.
Growing lesion or FDG uptake with known primary cancer are sufficient for the majority of authors. If a biopsy is done the risk of catecholamine release increases.
Nevertheless,
it can be useful to make a biopsy proven diagnosis in oncology and we have done this choice performing for all patients a biopsy in the same time than the thermal ablation with co axial system.
*Protection of surrounding organs:
It can be necessary to protect surrounding organs.
Bowels are the most common adjacent structures and need to be protected carefully (Fig 4).
Thermal isolation is in rule not necessary for kidney ,
liver ,
pancreas or vessels (inferior vena cava,
aorta).
Protection is preferentially performed after having placed the thermal ablation device.
We use a 22G needle close to the structure that need protection.
2 methods are available,
hydro or aero dissection using carbonic gas or room air.
No ionic fluid will be used for RFA and contrast may be added for cryoablation in order to differentiate it from ice ball.
Fluid or gas are injected slowly and carefully with several CT controls.
*Embolization of the needle track:
We usually perform embolization of needle track with gelfoam in order to decrease risk of bleeding (Fig 5) has done in some cases of liver,
lung or kidney biopsies.
-Complications:
*Hypertensive crisis
It’s defined as an acute increase in blood systolic pressure > 180mm hg or a diastolic pressure > 110 mm hg.
It’s the most frequent and common complication during this kind of procedure (Fig 6).
Hypertensive crisis has been described in 53%5 and 57%13 of cases in the two largest cohorts in the literature.
It can be delayed with use of cryotherapy due to release of cathecholamine during the thaw.
It can result in cardiologic damages and arrhythmia14.
Tako Tsubo syndrome has been exceptionally reported15.
Hypertensive crisis can be managed by anti hypertensive medication (see chap cathecholamine release).
*Adrenal insufficiency:
Adrenal function is impaired when more than 90 % of functional adrenal tissue is destroyed.
Consultation before and after the procedure can be useful for patient with a high risk of adrenal insufficiency especially in case of bilateral adrenal ablation,
solitary adrenal gland or history of adrenal radiotherapy.
In case of this complication,
patients are treated with prednisone.
- Follow up:
Success is defined by the absence of tumor contrast enhancing on CT or MRI.
There is actually no guideline for follow up modality16.
We have made the choice to perform a CT with contrast injection immediately after the procedure and to control thereafter patients as scheduled by their primitive cancer (Fig 7)
- Results:
Adrenal thermal ablations have promising results.
The major limitations are the lack of long term follow up and the small number of patients included in the literature.
Technical success rates range between 94%13 and 96%5 in recent studies.
Main results are resumed in table 1 (Fig 8).
Apart hypertensive crisis ,
complication rate is low and most of them are grade 3 or less using clavien dido classification.
No procedure related death has been reported.