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36 Liver Ablation
Percutaneous ethanol injection (PEI) has fallen out of use in the treatment of early HCC as multiple studies have demonstrated superiority of RFA ablation compared to PEI [36]. However, PEI still has a role as it is often used for liver sclerosis and treatment of symptomatic hepatic cysts. It can be done in a single or multiple sessions [37]. The procedure itself involves percutaneously accessing the cyst, aspirating the contents, and then injecting alco­hol that is retained for a period of time prior to removal. The procedural goal is symptomatic relief even if the actual cystic cavity is not completely destroyed. Unique side effects include hypotension and the signs and symp­toms of alcohol intoxication such as nausea, dizziness, and ushing.
Trans-arterial embolization, including both chemoembo­lization and radioembolization, has been a dening role of interventionists in the treatment of HCC and liver metastasis. These techniques are discussed in Chaps. 34 and 35, respectively.
Prior to the procedure, the patient should have crosssec­tional imaging (CT or MRI) to delineate the target lesion, the anatomy, evaluate a safe window, determine ideal ablative modality, as well as assess potential complications and rem­edies. Patient with increased risk for infections, or hepatic abscess (those with prior sphincterotomy or biliary-enteric anastomosis), should be premedicated with an antibiotic prophylaxis regimen. Immediately prior to procedure, it should also be determined if the patient will need a hydrodissection.
401
36.2a). For HCC, contrast-
enhanced arterial phase images are often needed to visualize the tumor. The ablation zone consists of the tumor with a 5–10-mm rim of healthy tissue (safety margin). The number of probes, length, and amount of energy delivered will vary depending on the size of the desired ablation zone, manufacturer
-
ogy used.
3. If hydrodissection is needed, any device with an initial sharp needle that can be exchanged for a blunt introducer may be used to access the space between the tumor and organ at risk. The blunt introducer can be upsized to a catheter through
-
eter can be removed or left in place in case more
place as they interfere with the ablation.) Some cases may require multiple areas of hydrodissec­tion. Balloon interposition and biliary lavage are additional protective techniques.
4. The thermal ablation probe is advanced under
36.2b). The probes can be
advanced into the lesion or on each side (bracket technique). Computer software is sometimes used to help plan the trajectory. Once positioned, some devices allow the probes to be placed in tissue-lock mode preventing respiratory motion from dislodg-
The How to: Radiofrequency and Microwave Ablation
1. Patients can be placed under general anesthesia or conscious sedation. Some patients may have pain and discomfort due to the positioning or the abla­tion itself. Patients are usually placed supine or left lateral decubitus with the right arm out of the way. Ultrasound is often used for needle positioning, although with RFA the “gas out” (gas emitted by the burning of tissues) limits its value once the abla­tion has started. RFA requires grounding pads be placed on the patient’s thigh due to the electrical current.
2. Conventional computed tomography (CT), cone beam CT (CBCT), or ultrasound in combination or alone have been used for image guidance during ablations. Imaging is typically obtained at the time of the procedure once the patient is positioned to
of adequate probe positioning is essential prior to energy delivery. Needless to say, large vessels and organs, such as adrenal, kidney, and bowel, should be outside the projected ablation zone.
5. With MWA and some RFA devices, ablation is per-
a certain amount of time depending on the size of the desired ablation zone. For most RFA machines, however, tissue impedance is used to determine when ablation is complete. Once char is achieved, the impedance goes up and treatment is complete. Repeat imaging with and without contrast should be performed to ensure adequate tumor coverage including a safety margin appropriate for the type of tumor being treated (generally wider for meta­static disease). Note that most probes can coagulate the tract as they are being removed. If a second ablation is required, the probe may be repositioned and the process repeated.
6. removed, and imaging is repeated to rule out com-
36.2c).
402
J. Ton et al.
Fig. 36.2 A 79-year-old male with hepatitis B and HCC undergoing microwave ablation therapy for a hepatic segment 6 lesion. (a) Pre-ablation,
(b) ablation probe positioning, (c) post-ablation, and (d) 6-month follow-up images are shown demonstrating good treatment response
lowed up clinic visits can be performed every 3months for
Key Point
Complications:
the rst year, every 6 months for the second year, and as appropriate thereafter.
• Bleeding
• Tumor seeding
• Hepatic infarction
• Infection (peritonitis, abscess)
• Bile duct injury or bile leak
• Pneumothorax
• Pleural effusion or hemothorax
• Skin burns
For post-procedural care after thermal ablation, it is customary for patients to stay overnight for observation and pain control. Routine post-procedure labs are not needed. Patients are typically discharged the next day with plans to follow up with a clinic visit at 1month, which should include labs and imaging to assess response (see Fig. 36.2d). If indicated, surveillance imaging and fol-

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13. Ni JY, Xu LF, Sun HL, Zhou JX, Chen YT, Luo JH.Percutaneous ablation therapy versus surgical resection in the treatment for early­stage hepatocellular carcinoma: a meta-analysis of 21,494 patients. JCancer Res Clin Oncol. 2013;139(12):2021–33.
14. Hemming AW, Cattral MS, Reed AI, Van Der Werf WJ, Greig PD, Howard RJ. Liver transplantation for hepatocellular carcinoma. Ann Surg. 2001;233(5):652–9.
15. Iwatsuki S, Starzl TE, Sheahan DG, Yokoyama I, Demetris AJ, Todo S, etal. Hepatic resection versus transplantation for hepato­cellular carcinoma. Ann Surg. 1991;214(3):221–8; discussion 8–9.
16. Hoffmann AC, Gerken GG.Hepatocellular cancer: new kids on the block. Gastrointest Tumor. 2014;1(4):195–200.
17. Lencioni R, Llovet JM, Han G, Tak WY, Yang J, Guglielmi A, et al. Sorafenib or placebo plus TACE with doxorubicin-eluting beads for intermediate stage HCC: the SPACE trial. J Hepatol. 2016;64(5):1090–8.
18. Llovet JM, Ricci S, Mazzaferro V, Hilgard P, Gane E, Blanc JF, et al. Sorafenib in advanced hepatocellular carcinoma. N Engl JMed. 2008;359(4):378–90.
19. Gutierrez JA, Gish RG.Efcacy of combination treatment modali­ties for intermediate and advanced hepatocellular carcinoma: intra­arterial therapies, sorafenib and novel small molecules. Transl Cancer Res. 2013;2(6):460–71.
20. Bruix J, Qin S, Merle P, Granito A, Huang YH, Bodoky G, et al. Regorafenib for patients with hepatocellular carcinoma who progressed on sorafenib treatment (RESORCE): a ran­domised, double-blind, placebo-controlled, phase 3 trial. Lancet. 2017;389(10064):56–66.
21. Kudo M. Immune checkpoint blockade in hepatocellular carci­noma: 2017 update. Liver Cancer. 2016;6(1):1–12.
22. Trojan J, Waidmann O.Role of regorafenib as second-line therapy and landscape of investigational treatment options in advanced hepatocellular carcinoma. JHepatocell Carcinoma. 2016;3:31–6.
23. Amendolara M, Bucca D, Barbarino C, Romano MF, Marino G, Zucchelli M, et al. Surgical management of symptomatic simple hepatic cysts. G Chir. 2012;33(1–2):17–20.
24. Livraghi T, Solbiati L, Meloni F, Ierace T, Goldberg SN, Gazelle GS. Percutaneous radiofrequency ablation of liver metastases in potential candidates for resection: the “test-of-time approach”. Cancer. 2003;97(12):3027–35.
25. Mulier S, Mulier P, Ni Y, Miao Y, Dupas B, Marchal G, et al. Complications of radiofrequency coagulation of liver tumours. Br JSurg. 2002;89(10):1206–22.
26. Hoffmann R, Rempp H, Schmidt D, Pereira PL, Claussen CD, Clasen S.Prolonged antibiotic prophylaxis in patients with bilio­enteric anastomosis undergoing percutaneous radiofrequency abla­tion. JVasc Interv Radiol. 2012;23(4):545–51.
27. Curley SA, Izzo F, Ellis LM, Nicolas Vauthey J, Vallone P.Radiofrequency ablation of hepatocellular cancer in 110 patients with cirrhosis. Ann Surg. 2000;232(3):381–91.
28. Zhou Y, Zhao Y, Li B, Xu D, Yin Z, Xie F, etal. Meta-analysis of radiofrequency ablation versus hepatic resection for small hepato­cellular carcinoma. BMC Gastroenterol. 2010;10:78.
29. Lee KF, Wong J, Hui JW, Cheung YS, Chong CC, Fong AK, etal. Long-term outcomes of microwave versus radiofrequency ablation for hepatocellular carcinoma by surgical approach: a retrospective comparative study. Asian J Surg. 2017;40(4):301–8. 2016. Epub 2016 Feb 24.
30. Poulou LS, Botsa E, Thanou I, Ziakas PD, Thanos L.Percutaneous microwave ablation vs radiofrequency ablation in the treatment of hepatocellular carcinoma. World JHepatol. 2015;7(8):1054–63.
31. Kim YS, Rhim H, Paik SS.Radiofrequency ablation of the liver in a rabbit model: creation of articial ascites to minimize collateral thermal injury to the diaphragm and stomach. JVasc Interv Radiol. 2006;17(3):541–7.
32. Laeseke PF, Sampson LA, Brace CL, Winter TC 3rd, Fine JP, Lee FT Jr. Unintended thermal injuries from radiofrequency abla­tion: protection with 5% dextrose in water. AJR Am JRoentgenol. 2006;186(5 Suppl):S249–54.
33. Laeseke PF, Sampson LA, Winter TC 3rd, Lee FT Jr. Use of dextrose 5% in water instead of saline to protect against inad­vertent radiofrequency injuries. AJR Am J Roentgenol. 2005; 184(3):1026–7.
34. Lee SJ, Choyke LT, Locklin JK, Wood BJ.Use of hydrodissection to prevent nerve and muscular damage during radiofrequency abla­tion of kidney tumors. JVasc Interv Radiol. 2006;17(12):1967–9.
35. Yang Y, Wang C, Lu Y, Bai W, An L, Qu J, et al. Outcomes of ultrasound-guided percutaneous argon-helium cryoabla­tion of hepatocellular carcinoma. J Hepatobiliary Pancreat Sci. 2012;19(6):674–84.
36. Brunello F, Veltri A, Carucci P, Pagano E, Ciccone G, Moretto P, et al. Radiofrequency ablation versus ethanol injection for early hepatocellular carcinoma: a randomized controlled trial. Scand JGastroenterol. 2008;43(6):727–35.
37. Yang CF, Liang HL, Pan HB, Lin YH, Mok KT, Lo GH, et al. Single-session prolonged alcohol-retention sclerotherapy for large hepatic cysts. AJR Am JRoentgenol. 2006;187(4):940–3.
Lung, Kidney, andBone Ablation
DavidM.Mauro

Pathophysiology

Lung Cancer
Within the United States, primary lung cancer is the second most common cancer among men and women (behind pros­tate and breast, respectively), but is the number one cause of cancer-related death with an estimated 158,080 deaths and 224,390 new cases in 2016 [1]. While the incidence of lung cancer has been declining, it still accounts for approximately one in four cancer deaths. Primary lung cancer is classied as either small cell or non-small cell lung cancer, with non­small cell lung cancer encompassing 83% of cases.
Key Point
Subtypes of lung cancer:
• Non-small cell – Adenocarcinoma – Squamous cell – Large cell
• Small cell
Primary lung cancer is often asymptomatic in its early stages but may manifest with persistent cough, bloody spu­tum production, pain, increasing shortness of breath, or recurrent pulmonary infections [1]. Cigarette smoking remains the most important risk factor [1]. Other environ-
D. M. Mauro (*) University of North Carolina, Department of Radiology, Chapel Hill, NC, USA e-mail: david_mauro@med.unc.edu
37
Table 37.1 Simplied TNM staging system for lung cancer [2]
Lung cancer TNM staging system
T (primary tumor)
T0 No primary tumor or carcinoma in situ T1
Tumor 3cm
T2
Tumor >3 but 5cm or tumor involving the visceral pleural, main bronchus, or with atelectasis to the hilum
T3
Tumor >5cm but 7cm or tumor invading the chest wall, pericardium, phrenic nerve, or separate tumor nodule (s) in the same lobe
T4
Tumor 7cm or tumor invading the mediastinum, diaphragm, heart, great vessels, recurrent laryngeal nerve, carina, trachea, esophagus, spine, or tumor nodule(s) in different ipsilateral lobe
N (regional lymph nodes)
N0 No regional node metastases N1 Metastases in ipsilateral pulmonary or hilar lymph nodes N2 Metastases in ipsilateral mediastinal or subcarinal lymph nodes N3 Metastases in contralateral mediastinal or hilar lymph nodes or
supraclavicular lymph nodes
M (distant metastasis)
M0 No distant metastases M1 Distant metastases including malignant pleural or pericardial
effusions
mental exposures, such as radon gas, pollution, secondhand smoke, asbestos, and certain metals and chemical exposures, are also signicant risk factors [1].
Non-small cell lung cancer is staged using the TNM (tumor, node, metastasis) staging system from the American Joint Committee on Cancer [2]. In 2017, Detterbeck et al. published the eighth edition of lung cancer stage classica­tion. A simplied version of the staging system is depicted in Table37.1.
The lungs are a common site for metastatic disease, with pulmonary metastases found during autopsy in 50% of patients with a cancer-related death in a 1000 patient series [3]. The presence of pulmonary metastasis usually indicates widespread dissemination of the primary cancer. Pulmonary metastases are frequently asymptomatic and are typically found during surveillance imaging or at initial diagnosis.
© Springer International Publishing AG, part of Springer Nature 2018 N. A. Keefe et al. (eds.), IR Playbook, https://doi.org/10.1007/978-3-319-71300-7_37
405
406
D. M. Mauro
Renal Cell Carcinoma
The American Cancer Society estimated that there would be nearly 63,000 new diagnoses of kidney cancer in 2016, the vast majority being renal cell carcinoma (with the remaining predominantly being urothelial cancer or Wilms tumor) [1]. The incidence of kidney cancer had been increasing over time, partially attributed to increased abdominal imaging and incidental diagnosis; however, rates have recently stabilized [1]. There are multiple sub­types of renal cell carcinoma with the clear cell subtype being the most common. Small renal cell carcinomas are typically asymptomatic. Later stage tumors can preset with hematuria, abdominal or ank pain, ank mass, weight loss, and/or fatigue. Risk factors include obesity, cigarette smoking, hypertension, chronic kidney disease, environ­mental exposures, and certain genetic conditions such as von Hippel-Lindau disease or hereditary papillary renal cell carcinoma [1].
Key Point
Subtypes of renal cell carcinoma:
• Clear cell (most common).
• Papillary.
• Chromophobe.
• Collecting duct, medullar, and sarcomatoid are rare.
Renal cell carcinoma is staged using the TNM staging system from the American Joint Committee on Cancer [4]. The seventh edition of the staging system, updated in 2010 is shown in Table37.2.
Table 37.2 Simplied TNM staging system for renal cell carcinoma [4]
Renal cell carcinoma TNM staging system
T (primary tumor)
T0 No primary tumor T1
Tumor conned to the kidney and 7cm T1a
Tumor 4cm
T1b
Tumor >4cm but 7cm T2 Tumor conned to the kidney and >7cm T3 Tumor with extrarenal extension or involvement of the renal
vein or inferior vena cava
T4 Tumor extends through Gerota’s fascia
N (regional lymph nodes)
N0 No regional node metastases N1 Regional lymph node metastases
M (distant metastasis)
M0 No distant metastases M1 Metastases present in distant lymph nodes or organs
Bone Lesions
Osteoid osteomas are benign osseous tumors that account for 10–12% of benign bone tumors [5]. While the lesions can present at almost any age, 85% of the cases have symptom onset between 5 and 24years of age, with a male predomi­nance. Osteoid osteomas classically present with pain, worse at night, which is relieved by nonsteroidal anti-inammatory drugs [6]. If untreated, lesions can lead to growth distur­bance, muscle atrophy, and clinical disability. The femur and tibia are the most common sites of disease [7].
Metastatic bone lesions are common in patients with pri­mary breast, prostate, and lung cancer [8]. Bone metastases can present with pain, pathologic fracture or can be found incidentally on serial imaging. In cases of intractable pain or impaired mobility, metastases result in decreased quality of life and performance status.

Clinical Indication

Lung Cancer
Chest CT is the initial study of choice for the evaluation of a patient with suspected primary lung cancer or pulmonary met­astatic disease. Primary lung cancer often presents as a solitary pulmonary nodule or hilar mass. Primary benign and malig­nant lesions can have similar imaging ndings; however, cer­tain imaging ndings suggest malignancy, including size and lesion margins [9]. The larger the nodule, the higher risk of cancer, with a 10–20% risk of cancer if the nodule measures approximately 8 mm. Nodules with a speculated (jagged or sunburst) margin are more likely to be cancer than a smooth contour. Metastatic lesions are often rounded single or multi­ple nodules of various sizes scattered throughout the lung.
In high-risk patients with characteristic lesions, biopsy is frequently not required prior to treatment. Treatment options include surgical resection, radiation therapy, chemotherapy, and percutaneous ablation.
Kidney Cancer
Physical examination does not play a signicant role in diag­nosis of renal cell carcinoma. However, a thorough physical exam can detect signs of advanced or metastatic disease. Abdominal ultrasound or CT frequently detects renal masses incidentally. Non-cystic renal masses are characterized with CT or MRI utilizing a multiphase renal mass protocol. On CT, small renal cell carcinomas tend to be homogeneous on non-contrast imaging; however, larger lesions can be hetero­geneous secondary to necrosis and/or hemorrhage [9]. The majority of renal cell carcinomas show avid enhancement. Masses are best visualized during the nephrographic phase
37 Lung, Kidney, andBone Ablation
407
when the normal renal parenchyma is homogeneously enhancing. Enhancement is similar with MRI; however, non­contrast imaging can suggest subtype histology.
Historically, renal mass biopsies were rarely performed due to the high false-negative rate, risk of complications, risk of tumoral seeding of the biopsy tract, and high accuracy of cross-sectional imaging. Recently, renal biopsy has become more common, as small renal masses have been found to be benign in approximately 20% of patients [10], and biopsy techniques have improved.
Bone Lesions
Osteoid osteomas are suspected based on patient age, history of nocturnal pain relieved by nonsteroidal anti- inammatories, and the lack of other physical exam ndings. On CT or plain lm, an osteoid osteoma appears as a lucent, oval nidus that is usually less than 1.5cm in diameter with an adjacent perios­teal reaction causing thickening/sclerosis of the cortex [11]. A central density may be seen within the nidus. There is fre­quently adjacent soft tissue swelling. While osteoid osteomas are benign and may spontaneously resolve, most experts rec­ommend treatment to prevent long- term sequelae [12].
Bone metastases may be detected incidentally, on imaging for surveillance or metastatic work-up or as part of a diagnos­tic evaluation for patient-directed complaints. The lung, breast, and prostate represent the most common primary can­cers, with osseous metastases found in up to 85% of patients at autopsy [8]. Most metastatic lesions are asymptomatic, but they may present with pain or pathologic fracture. Breast and prostate metastases are most commonly blastic, while lung metastases are more often lytic lesions. Plain lm may dem­onstrate the lytic or blastic changes from metastatic disease, but CT is better for evaluating disease extent. MRI also dem­onstrates bone marrow changes at sites of bony metastasis. Nuclear medicine bone scans provide a whole-body overview and will show increased uptake (blastic lesions) or photope­nic areas (lytic lesions) with high sensitivity.

Conventional Therapy

Treatment algorithms for most cancers are complex and mul­tifactorial; treatment decisions are frequently made through multidisciplinary tumor boards. There is consensus on some principles on the role of ablation.
Lung Cancer
Surgical resection is the gold standard treatment for early stage (stage I and II) non-small cell lung cancer [13]. Surgical
resection consisting of lobectomy with lymph node dissec­tion demonstrates the best disease-free survival in patients with early stage non-small cell lung cancer [14]. Unfortunately, approximately two-thirds of patients are med­ically inoperable at diagnosis [15]. For these patients, stereo­tactic ablative radiotherapy (SABR) and percutaneous ablation can be considered for denitive therapy. For patients with locoregional recurrence after surgery, repeat surgery, SABR, or percutaneous ablation can be considered for con­tinued treatment. Current National Comprehensive Cancer Network guidelines recommend SABR for medically inop­erable stage IA non-small cell lung cancer [13]. However, percutaneous ablation is noted to be an option for select patients. To date, there has not been a head to head trial com­paring SABR to percutaneous ablation.
Key Point
Stereotactic ablative radiotherapy and percutaneous ablation are the denitive treatment option for medi­cally inoperable non-small cell lung cancer.
Kidney Cancer
Surgery remains the gold standard for small renal masses [16]. Current National Comprehensive Cancer Network guidelines recommend partial nephrectomy as the preferred treatment for stage 1A kidney cancer. The guidelines include ablation as a primary treatment option in select patients. Ablation can be performed either laparoscopically or percu­taneously. While laparoscopic cryoablation has shown to have fewer complications and result in shorter hospital stays compared with laparoscopic or robotic partial nephrectomy, the ablation group also had higher rates of local tumor pro­gression and metastases [17]. A large retrospective study from Thompson etal. demonstrated similar recurrence-free survival between partial nephrectomy, percutaneous cryoab­lation, and percutaneous radiofrequency ablation [18]. However, metastases-free survival was higher for both par­tial nephrectomy and cryoablation compared to radiofre­quency ablation. The partial nephrectomy group had superior overall survival; however, the population was younger and healthier compared to the ablation groups. A 2008 meta­analysis comparing percutaneous to laparoscopic tumor ablation using both cryoablation and radiofrequency ablation demonstrated higher primary effectiveness within the surgi­cal group, 94% versus 87%, respectively [19]. However, with secondary effectiveness, the percutaneous ablation group achieved 95% effectiveness. Additionally, major com­plications were 7% for laparoscopic ablation compared to 3% for percutaneous ablation.
408
Key Point
Renal mass ablation is indicated for masses less than
4cm in patients who are:
• Poor surgical candidates
• In need of nephron-sparing treatment due to medi­cal renal disease, prior surgery, or risk of future car­cinoma (genetic syndrome)
D. M. Mauro
Table 37.3 Hallmark papers describing the use of ablative technolo-
gies in various organs
Ablation type Organ Year Hallmark paper Radiofrequency Liver 1990 McGahan etal. [23], Rossi etal. [24] Radiofrequency Bone 1992 Rosenthal etal. [25] Radiofrequency Lung 1995 Goldberg etal. [26] Cryoablation Kidney 1995 Uchida etal. [27] Radiofrequency Kidney 1997 Zlota etal. [28]

Interventional Therapy

Bone Lesions
There are a vast number of treatment options for bone tumors, including surgery, external beam radiation, ablation, hormonal therapy, and chemotherapy. Historically, surgery was performed for treatment of osteoid osteoma. However, due to similar recurrence rates, quicker recovery, and favor­able complication prole, radiofrequency ablation has become the preferred treatment [7]. In a comparison between surgery and ablation, recurrence rate was 9% and 12%, respectively, which was not statistically signicant [20]. A subsequent literature review in 2013 concluded an average recurrence rate of 4.9% following ablation [21].
Key Point
Radiofrequency ablation is the preferred treatment for osteoid osteoma.
Traditionally, external beam radiation or surgery is the primary treatment for oligometastatic disease with chemo­therapy used for disseminated disease [7]. Surgery is typi­cally an option for pathologic fractures or impending pathologic fractures. While 60% of patients have pain relief following external beam radiation, the results are frequently temporary. Patients with recurrent pain after irradiation may not be candidates for further external beam radiation due to quantitative dose [6]. Pathologic compression frac­tures can be treated with a combination of radiofrequency ablation and vertebral augmentation using polymethyl methacrylate [22].
Percutaneous image-guided thermal ablation was rst described in the 1990s (Table 37.3). As technology has improved the safety and efcacy prole of percutaneous tumor ablation, it has become a common alternative to surgi­cal therapy. With a wide variety of modalities and technolo­gies available, there is a heterogeneity in ablation practice with signicant operator variability and preference. Below is a brief review of the more common ablation technologies.
Key Point
RFA=electrical current to produce heat. MWA=agitation of water molecules to produce heat. Cryoablation=cooling cells to cytotoxic temperatures. IRE=rapid alternating currents create holes in the cell
membrane to increase cell permeability.
Radiofrequency Ablation (RFA)
During radiofrequency ablation, an oscillating electrical cur­rent is created between an electrode (ablation probe) and grounding pad or between two electrodes [29]. Due to poor conduction of electricity within tissue, frictional heat is pro­duced from the owing electrical current causing ionic agita­tion in the adjacent tissue. Thermal conduction through the tissue creates a larger ablation zone [11]. Immediate cell death occurs between temperatures of 60 and 100°C. The ablation zone is limited by tissue dehydration and charring; however, newer technologies attempt to limit this from occurring during the ablation process.
Key Point
Radiofrequency ablation combined with vertebro-
plasty or kyphoplasty can be used to treat compression
fractures secondary to osseous metastatic disease.
Microwave Ablation (MWA)
Microwave energy agitates water molecules, creating fric­tional heat and cell death [11]. During ablation, an oscillat­ing electromagnetic eld is created by the antennae (ablation probe). Distinct from radiofrequency ablation, an electrical current is not involved; therefore, the ablation continues to
37 Lung, Kidney, andBone Ablation
409
be effective in tissues with poor electrical conductivity, [29] and grounding pads are not necessary [15].
Heat sink occurs when adjacent blood vessels dissipate thermal energy thereby interfering with the tissue heating or cooling [29]. Heat sink leads to a decrease in the size of the ablation zone with vessels greater than 3mm thought to be signicant causes of heat sink, affecting the ablation zone size. Microwave ablation appears to be less affected by heat sink compared to other thermal ablation modalities.
Cryoablation
In contrast to radiofrequency and microwave ablation, cryo­ablation induces cell death by cooling cells to cytotoxic tem­peratures [29]. Cryoablation utilizes the Joule-Thomson effect, a decrease in temperature resulting from a change in gas pressure. The tip of a cryoablation probe can reach a tem­perature of 185 °C [11]. Cryoablation procedures typically utilizes two freeze-thaw cycles, with an active freezing period induced by the cryoablation probe followed by a pas­sive thaw period [30].
Irreversible Electroporation (IRE)
Unlike the three ablation modalities described above, irre­versible electroporation is a nonthermal process. Rapid elec­trical impulses create microscopic pores within the cellular membrane resulting in increased membrane permeability and cell death [11]. An advantage of irreversible electropora­tion is that the target is the cell membrane, therefore, theo­retically sparring connective tissue such as the collecting system within the kidney. However, the electrical impulses can also result in cardiac arrhythmia and muscle contrac­tions; therefore, cardiac monitoring and general anesthesia with neuromuscular blockade are necessary. As a nonthermal ablation modality, irreversible electroporation is not suscep­tible to heat sink.
Modality choice is driven by tissue type, specic pathol­ogy, lesion size, operator preference, and modality availabil­ity. Radiofrequency ablation, microwave ablation, and cryoablation are all used within the lung, kidney, and bone. Microwave ablation may be preferred in larger tumors. Irreversible electroporation is not as common and is fre­quently reserved for perivascular lesions or lesions adjacent to the renal collecting system.
Lung Cancer
Lung ablation is an option for patients with early stage (sur­gically resectable) disease who are not surgical candidates,
either due to poor pulmonary reserve or medical comorbidi­ties (Fig.37.1). Ablation has also been used in patients with oligometastatic disease who cannot undergo surgical metas­tastectomy. Additionally, ablation can be considered for dis­ease recurrence within a previous treatment zone or as symptomatic palliation from tumor burden. The majority of the data uses radiofrequency ablation; however, microwave ablation, cryoablation, and irreversible electroporation have produced positive outcomes in the literature [31]. In 2000 Dupuy etal. reported the rst series of radiofrequency abla­tion for inoperable non-small cell lung cancer [32]. Tissue characteristics within the lung provide a favorable prole for thermal ablation as the lung parenchyma provides heat insu­lation and is a poor electrical conductor [31].
Outcome data for lung ablation is variable throughout the literature due to variance in tumor size and ablation modal­ity. In 2008, a review of 17 reports, which included both pri­mary and metastatic disease, demonstrated rates of complete ablation ranging from 38% to 97% following radiofrequency ablation [33]. Multiple reports have shown excellent success with ablation of tumors smaller than 2 cm, with complete ablation ranging from 78% to 96% [34]. In a recent review of the literature, overall survival rates at 1, 3, and 5years were reported between 77.1% and 97.7%, 36% and 72.9%, and
20.7% and 55.7%, respectively [35]. Multiple reports have shown tumor size, tumoral contact to blood vessels greater than 3mm, and ground-glass ablation margin to be predic­tive factors in recurrence. In a 153-patient series undergoing radiofrequency ablation including stage I non-small cell lung cancer and colorectal pulmonary metastatic disease, 1-, 3-, and 5-year survival was found to be 78%, 36%, and 27% for primary cancer and 87%, 57%, and 57% for metastatic dis­ease [36]. Additionally, the 1-, 3-, and 5-year local tumor progression-free rates was 83%, 57%, and 47% for tumors 3cm or smaller but 45%, 25%, and 25% for larger tumors.
Kidney Cancer
Percutaneous renal mass ablation is considered for patients with small renal masses (less than 4 cm, T1a tumors, Fig.37.2) [30]. Ideal lesions are noncentral and without met­astatic disease, renal vein invasion, or extension through Gerota’s fascia. Ablation may be favored over surgical resec­tion in patients who are poor surgical candidates due to comorbidities, chronic kidney disease necessitating maximal nephron preservation, or hereditary syndromes with a high risk of subsequent renal carcinomas. The American Urological Association and International Consensus panels support ablation for lesions less than 4cm, among other indi­cations [37].
There is no prospective, randomized controlled trial com­paring partial nephrectomy to ablation. In 2015 Thompson
410
D. M. Mauro
Fig. 37.1 An 88-year-old male with a 2.7 cm left lower lobe biopsy
proven non-small cell lung cancer. The lesion was found during work­ up for prolonged cough. The patient declined surgical intervention. (a, b) PET-CT demonstrating a 2.7 cm uorodeoxyglucose (FDG)-avid lesion in the left lower lobe. (c) Initial placement of two cryoablation
etal. compared partial nephrectomy, percutaneous cryoabla­tion, and percutaneous radiofrequency ablation with similar recurrence-free survival [18]. However, partial nephrectomy and percutaneous cryoablation demonstrated improved metastases-free survival compared with percutaneous radio­frequency ablation. In 2013 Atwell et al. retrospectively
probes with mild surrounding hemorrhage from placement. (d) Intra­procedural imaging showing ground-glass opacities surrounding the lesion representing the ablation zone. A small pneumothorax and effu­sion are noted. (e, f) Follow-up PET-CT 3-month post-ablation showing cavitation at the ablation site and no FDG avidity
reviewed recurrence of tumors less than 3cm treated with cryoablation and radiofrequency ablation [38]. At 1, 3, and 5 years, recurrence-free survival was found to be 97.3%,
90.6%, and 90.6%, respectively, for cryoablation and 100%,
98.1%, and 98.1%, respectively, for radiofrequency ablation. The complication rates were not statistically different
37 Lung, Kidney, andBone Ablation
411
Fig. 37.2 A 67-year-old male with a history of bilateral renal cell carci-
nomas status post partial nephrectomies found to have a new 1.4cm left renal cell carcinoma on surveillance imaging. (a, b) T1, contrast enhanced MRI in the arterial and nephrographic phases demonstrating a left-sided exophytic 1.4cm enhancing lesion consistent with a renal cell carcinoma. (c) Scout CT from the ablation procedure. The renal cell carcinoma appears as a hyperdense exophytic lesion. (d) Intra- procedural
imaging with two cryoablation probes. (e) Imaging after rst thaw cycle showing a hypodense ablation zone. (f) Two-month follow-up MRI, T1 post-contrast in the nephrographic phase with no enhancement or evi­dence of residual tumor. Note the hyperintensity in the ablation zone was present on pre-contrast T1 imaging and consistent with hemorrhage. (g) Three-year follow-up MRI, T1 post-contrast in the nephrographic phase. The ablation zone has scared with no evidence of enhancement