Type:
Educational Exhibit
Keywords:
Neoplasia, Cancer, Ablation procedures, Percutaneous, CT, Thorax, Lung
Authors:
D. Geat1, G. Cicchetti1, A. Ottavianelli1, A. Farchione1, A. del Ciello2, R. Iezzi1, A. R. Larici1, L. Bonomo1, R. Manfredi1; 1Rome/IT, 2Roma/IT
DOI:
10.1594/ecr2018/C-1152
Background
In patients with initial stage NSCLC,
i.e.
stage IA (T1ab N0),
surgery represents the first line treatment because its survival rate (about 50% at 5 years) is higher than any other treatment.
However,
in some cases surgery is not possible because of medical comorbidities or because of patients’ refusal.
In such patients,
alternative treatments are radiation therapy (including stereotactic body radiation therapy – SRBT) and thermal ablation – whether in the form of radiofrequency ablation (RFA),
microwave ablation or cryoablation.
RFA use in lung cancer was first reported by Dupuy in 2000 [1]; since then it emerged an effective treatment for both primary and secondary pulmonary malignancies.
In primary tumors,
its 3-year survival rates range in different studies between 47 and 60% [2].
RFA employs an electrode needle (figure 7A) which delivers a high frequency (400-500 kHz) sinusoidal current which passes between the electrode and grounding pads on the patient’s leg.
This alternating current produces ionic agitation in the tissues adjacent to the electrode which in turn causes local frictional tissue heating.
As a consequence,
thermal tissue damage and,
ultimately,
coagulation necrosis occur because temperatures higher than 60°C induce protein denaturation.
In order to provide long-lasting disease remission,
all of the visible disease needs to be ablated. The median reported rate of complete ablation described in literature ranges from 38% to 97% [3], with tumors smaller than 2 cm being successfully ablated with a single treatment in 78-96% of patients.
Furthermore,
RFA can be deemed a safe technique; its specific mortality rate ranges between 0.4% and 2.6% and its major complication rate (as defined by the Society of Interventional Radiology as one requiring remedial action or where the patient experiences significant morbidity) lies between 9.8 and 17.1% [4].
Radiological follow-up after RFA is of fundamental importance in order to assess the efficacy of the procedure and to allow early detection of recurrences; this latter aspect has crucial relevance because – when detected early by CT or PET follow-up – patients can often repeat the treatment.
Thermal ablation techniques are often reserved to larger hospitals,
therefore not all radiologists may have experience with these treatments.
However,
interpretation of post-treatment follow-up imaging is expected not only from thoracic radiologists in larger centers,
but also from general radiologists in smaller hospitals.
Familiarity with the most common CT patterns observed following RFA is therefore of fundamental importance for all radiologists in the management of these patients.