rad review of cardiovascular and interventional imaging Interventional oncology for RAD Magazine, 45, 533, 22 Gus Rottenberg Medical student University of Cambridge Renganaden Pyneeandee Senior clinical nurse Department of radiology, Cambridge University Hospitals NHS Foundation Trust Dr Miltiadis Krokidis Consultant vascular and interventional radiologist Cambridge University Hospitals NHS Foundation Trust [email protected]

Renal cell carcinoma (RCC) accounts for approximately 3% Figure 1 of all adult with an estimated 12.1 new cases per Set-up for CT-guided radiofrequency year for 100,000 of population in the western world.1,2 The with three electrodes. Note that one of the three incidence rate of sporadic RCC has increased in the last two electrodes is inserted via a coaxial needle where decades, mainly due to the increased use of cross-sectional previously a specimen was obtained. imaging but also due to obesity and smoking. Thoracic CT scans that were performed for other purposes may reveal asymptomatic small masses when the upper part of the abdomen is scanned, particularly in males in their sixth decade of life. Advanced stage RCC has a clear management pathway that mainly consists of nephrectomy or palliative treatment. The management of small, early stage, asymptomatic sporadic RCC is a bit more complex given that the behaviour of the lesion cannot be predicted. Masses that measure 2-3cm have metastatic potential and need to be managed accordingly. The general consensus is to assess the growth pattern with active imaging surveil- lance. A B When treatment is considered, surgical excision with either open or laparoscopic partial nephrectomy appears to Figure 2 be the gold standard approach, aiming to preserve as much (A) Appearance of the different insertion angles of healthy parenchyma as possible. Interventional oncology the three electrodes. (B) CT may offer another minimally invasive solution for these reconstructed pictures confirm that all three elec- patients with percutaneous image-guided ablation.3 The first trodes converge at the centre of the lesion. percutaneous image-guided ablation of a kidney mass was performed in 1998 utilising radiofrequency technology. Radiofrequency is based on the use of high frequency electric their continuous re-orientation within the oscillating field; current that causes oscillation of the tissue molecules and this movement increases their kinetic energy and is produces heat. When the temperature reaches 60ºC the tis- deposited in the tissue as thermal energy. Microwave has sue is destroyed. This technology is now established in the only recently been introduced in the percutaneous treatment 6 treatment of small renal masses with long-term results.4 of RCC, however it has produced some encouraging results. Another ablation modality that has been used for a num- RCC however is not only sporadic, it may also be hered- ber of years in the percutaneous image-guided treatment of itary and linked with the mutation of specific genes. The RCC is . The physical principle of cryoablation autosomal dominant mutation of the von Hippel-Lindau is based on the radical reduction of temperature that is (VHL) gene is the most common one. In such cases young achieved by the rapid expansion of a high pressure inert patients may present with multiple bilateral synchronous gas (mainly Argon) also known as the Joule-Thompson prin- RCCs. Preserving as much as possible of the healthy ciple. With temperature reduction direct cellular damage is parenchyma is of paramount importance in such patients in achieved both from osmotic dehydration of the cells but also order to delay haemodialysis and therefore minimally inva- due to the intracellular ice formation. Percutaneous cryoab- sive percutaneous ablation has a significant role. lation has also offered excellent long-term results in the Another group of patients that may benefit significantly management of small renal masses.5 from treatment with percutaneous ablation are patients that is another modality recently intro- underwent nephrectomy and develop a new RCC or a duced for the percutaneous treatment of RCC. Microwave metastatic lesion in the contralateral kidney, or those who is based on the use of an electromagnetic wave that causes develop an RCC in a single functioning kidney. In such continuous rotation of tissue water molecules. The non-equal patients percutaneous ablation offers a valid tumour control distribution of electric charge of the water molecules causes solution with preservation of the renal function.7 rad review of cardiovascular and interventional imaging

One of the main advantages of percutaneous ablation is that it may be performed under local anaesthesia and con- scious sedation, without need for a general anaesthesia. Laboratory and clinical assessment is required to assess the coagulation status of the patient and fitness in terms of posi- tion and access to the lesion. Anticoagulation needs to be stopped, as per standard percutaneous procedures and, in case of use of Warfarin, bridging with heparin is required. Image guidance is usually performed with CT as this is available in every radiology department and permits imaging in all planes. Ultrasound may be used for posterior exophytic lesions, however imaging is suboptimal as the exact distance with the bowel cannot be assessed. MRI would require spe- cific MR-compatible electrodes and the lack of space in the A B gantry adds a level of complexity without a clear benefit. Patients that will receive sedation will need to be fasted for six hours prior to the procedure. The protocol at Cambridge University Hospitals consists of admission at the radiology day unit a few hours prior to the procedure. The patients are transferred to a ward post procedure for overnight observation and discharged early the next morning, aiming for less than 24 hours’ stay in hospital. When the patients are in the CT room premedica- tion with 1000mg of paracetamol iv is administered and then conscious sedation with 1-4mg of midazolam and 50- 200µg of fentanyl, the moment prior to the ablation. Biopsy of the lesions needs to be obtained prior to ablation in all cases. Usually this is the first approach to the lesion that is then discussed in the MDM and a decision of treatment C D is made, but in the case that this pathway is not followed, ie for patients with VHL or metastatic disease, then a biopsy of the lesion prior to ablation is required. In such cases Figure 3 biopsy should be performed via a coaxial system that would (A) CT scan in arterial phase showing a mass in a also be used as access of the electrode, since bleeding post patient with single kidney and VHL syndrome. (B) biopsy might limit the delineation of the lesion borders. In Insertion of three electrodes for treatment. (C,D) case of contiguity with the bowel, hydro dissection with non- Immediate post-procedure non-contrast CT scan ionic solution needs to be considered, via a thin needle, to and four weeks post-procedure triple-phase scan displace the bowel and to insulate the lesion. confirm satisfactory result with preservation of the Ablation might be performed with a variety of modalities surrounding parenchyma. as mentioned, however it needs to be taken into account that renal tumours are not always spherical and this may pose a limitation to the use of a single electrode such as, short time in hospital. Interventional oncology appears to for example, in the case of microwave. What is usually more offer a valid alternative to surgery for patients with small realistic is to have to treat tumours that are ovoidal in size RCC. shape; an ovoidal shape may be achieved either with the use of three electrodes of cryoablation or with three References electrodes of radiofrequency ablation. Cryoablation would 1, European Network of Registries. Eurocim version 4.0. European require much more time, however, as there is need for a incidence database V2.3, 730 entity dictionary (2001), Lyon, 2001. period of thawing so the ablation cycles would require prob- 2, Ferlay J, Steliarova-Foucher E, Lortet-Tieulent J et al. Cancer incidence and mortality patterns in Europe: estimates for 40 countries in 2012. Eur ably 40-50 minutes. With the use of three radiofrequency J Cancer 2013;49(6):1374-403. ablation electrodes with alternating current the required 3, Krokidis M E, Orsi F, Katsanos K et al. CIRSE Guidelines on time is only 16 minutes. Percutaneous Ablation of Small Renal Cell Carcinoma. Cardiovasc Follow-up with triple-phase CT scan is required four Intervent Radiol 2017;40(2):177-91. 4, Psutka S P, Feldman A S, McDougal W S et al. Long-term oncologic out- weeks post ablation to assess if there is any residual enhanc- comes after radiofrequency ablation for T1 renal cell carcinoma. Eur Urol ing tissue. In case of incomplete lesion ablation a second 2013;63(3):486-92. session is required as soon as possible. If the ablation result 5, Georgiades C S, Rodriguez R. Efficacy and safety of percutaneous cryoab- is satisfactory, with lack of enhancement of the lesion, then lation for stage 1A/B renal cell carcinoma: results of a prospective, sin- gle-arm, 5-year study. Cardiovasc Intervent Radiol 2014;37(6):1494-99. follow-up with a triple-phase CT scan at six and 12 months 6, Yu J, Zhang G, Liang P et al. Midterm results of percutaneous microwave is required, and yearly thereafter for a total of five years. ablation under ultrasound guidance versus retroperitoneal laparoscopic Ablation offers excellent long-term oncologic results in the radial nephrectomy for small renal cell carcinoma. Abdom Imaging. locoregional treatment of RCC and needs to be offered to 2015;40(8):3248-56. 7, Krokidis M, Spiliopoulos S, Jarzabek M et al. Percutaneous radiofrequency every patient with tumour up to 4cm in diameter. The main ablation of small renal tumours in patients with a single functioning kid- advantage is the minimally invasive nature and the very ney: long-term results. Eur Radiol 2013;23(7):1933-39.