Physical Address
304 North Cardinal St.
Dorchester Center, MA 02124
Ablation of Renal Cell Carcinoma
In 2019, it is estimated that there will be more than 73,000 new cases and 14,770 deaths from renal cancer (including renal pelvis) in the United States. Renal parenchymal tumors (i.e., renal cell carcinoma [RCC]) account for most (85%) kidney cancers. Urothelial cancers of the renal pelvis (i.e., transitional cell carcinoma) account for most of the remaining cases. The incidence of RCC has increased on average by 2% to 3% per year for the past three decades. At present, more than 50% of RCCs are detected incidentally during imaging studies prompted by nonurologic complaints. Tumors detected incidentally are smaller (stage I; Table 101.1 ) at diagnosis and are often asymptomatic. Partial nephrectomy is the standard of care for small RCC and provides excellent results. Recurrence-free survival, cancer-specific survival, and overall survival rates for open or laparoscopic partial nephrectomy have been reported as greater than 95%, 97%, and 89%, respectively. Other alternative treatment options advocated by the American Urological Association (AUA) include active surveillance and thermal ablative therapies. In its most recent guidelines for management of small renal tumors, the AUA identified percutaneous thermal ablation as an alternative therapy for tumors smaller than 3 cm in selected patients.
TABLE 101.1
TNM Staging of Renal Cell Carcinoma by the American Joint Committee on Cancer
| Primary Tumor a | Node | Metastasis | |
|---|---|---|---|
| Stage I | T1 | N0 | M0 |
| Stage II | T2 | N0 | M0 |
| Stage III | T1 or T2 | N1 | M0 |
| T3 | N0 or N1 | M0 | |
| Stage IV | T4 | Any N | M0 |
| Any T | Any N | M1 |
T1: Tumor is 7 cm or less in greatest dimension and is limited to the kidney.
T1a: Tumor is 4 cm or less.
T1b: Tumor is greater than 4 cm but less than 7 cm.
T2: Tumor is more than 7 cm in greatest dimension and is limited to the kidney.
T3: Tumor extends into major veins or invades the adrenal gland, sinus fat, or perinephric fat, but does not extend beyond Gerota’s fascia.
T3a: Tumor invades the adrenal gland.
T3b: Tumor grossly extends into the renal vein or vena cava below the diaphragm.
T3c: Tumor grossly extends into the vena cava above the diaphragm.
T4: Tumor invades beyond Gerota’s fascia.
Ablative therapies can be thermal (heat-based or cold-based) or nonthermal (irreversible electroporation). The technologies most widely used in clinical practice for ablation of renal tumors are radiofrequency ablation (RFA) ( Figs. 101.1, 101.2, and 101.3 ) and cryoablation (CA) ( Figs. 101.4, 101.5, and 101.6 ). Microwave ablation (MWA), irreversible electroporation (IRE), laser, and high-intensity focused ultrasound technologies are in various stages of experimental or early clinical application for treating renal tumors. With any ablative technique, once the tumor is ablated, it is left in situ. This is a departure from the basic oncologic surgical principle of excision with clear margins. For ablation technology to be considered a clinically acceptable alternative to extirpation, it must be reliable and completely destroy all viable tumor. There must also be a means of imaging and monitoring the area of ablation to preserve and protect surrounding vital structures while ensuring complete tumor destruction. Thermal ablation of renal tumors can be performed either intraoperatively or percutaneously. Historically, RFA has been used most commonly for percutaneous image-guided ablation, whereas CA has been used most commonly in open or laparoscopic approaches. More recently, small-diameter cryoprobes have become available for percutaneous use, resulting in an increasing number of percutaneous cryoablation (PCA) procedures. At the same time, more urologic surgeons have adopted intraoperative RFA over CA, resulting in an increasing number of laparoscopic RFA procedures.
(Top row) A 64-year-old woman with multiple medical comorbid conditions was found to have a 1.2-cm, solid, enhancing mass involving the lateral aspect of the left kidney. (Center row) The patient was treated with computed tomography (CT)-guided percutaneous radiofrequency ablation. A needle was placed between the kidney and the colon to create hydrodissection. The needle was pulled back during the ablation to avoid heat conduction through the needle with resultant thermal injury of the skin. (Bottom row) Immediately after the ablation, axial contrast-enhanced CT images demonstrate high-density changes within the tumor, lack of enhancement indicating the margin of ablation zone, and a general reduction in the size of the exophytic tumor.
Copyright Kamran Ahrar, MD.
Follow-up unenhanced (left) and contrast-enhanced (right) axial computed tomography images of a patient (who underwent radiofrequency ablation) at 1, 6, 12, and 24 months demonstrate the evolution of postablation changes, including persistent high-density material in the ablation zone, lack of enhancement, and a thin halo of soft tissue density in the perinephric fat.
Copyright Kamran Ahrar, MD
(Top) A 42-year-old woman was diagnosed with bilateral solid, enhancing renal tumors. She also had bilateral renal cysts and multiple pancreatic cysts. A genetic workup confirmed diagnosis of von Hippel-Lindau disease. She required a right nephrectomy for a large renal cell carcinoma that had replaced most of the right kidney. Two separate tumors in the left kidney were treated with percutaneous radiofrequency ablation. (Bottom) Axial computed tomography images of this patient at 2 years postprocedure demonstrate no enhancement in the ablation zones in the left kidney.
Copyright Kamran Ahrar, MD.
A 68-year-old man with multiple medical comorbid conditions was found to have a 5.2-cm mass involving the upper pole of his left kidney. He was referred for percutaneous cryoablation. (A)–(C), Axial (A), sagittal (B) and coronal (C) computed tomography (CT) images show 5.2-cm mass involving the upper pole of his left kidney. (D)–(F) Preprocedure prophylactic embolization of the renal mass. (D) Digital subtraction angiogram shows a hypervascular mass involving the upper pole of the left kidney. (E) Sagittal CT angiogram delineates the arterial anatomy. Embolization was performed using 500-micron particles. (F) Postembolization digital subtraction angiogram shows vanishing of the hypervascular lesion and stasis in the embolized vessels. (G)–(L) Cryoablation of the left renal mass. (G), (H), and (L) Axial images show four of the six cryoprobes used to treat the lesion. Note the patient was placed on the ipsilateral side to avoid interposition of aerated lung during the probe insertion given that the lesion is in the upper pole of the kidney. (J) Axial CT image shows the needle used for hydrodissection. (M)–(O) Axial CT images immediately after the procedure show the ablation zone with adequate safety margin and no evidence of bleeding. (P)–(R) Follow-up contrast-enhanced CT 3 months after the ablation. Axial (P), sagittal (Q), and coronal (R) CT images show lack of enhancement in ablation zone involving the upper pole of patient’s left kidney.
Copyright Kamran Ahrar, MD.
(A) A 53-year-old man with a history of esophageal cancer was found to have a 3.6-cm left renal tumor. Biopsy showed renal cell carcinoma, papillary type 1. (B) Axial computed tomography (CT) image of the kidney during cryoablation shows three of the four cryoprobes engulfed in a low-density iceball. (C) Immediately after two freeze-thaw cycles, contrast-enhanced CT showed active extravasation and associated retroperitoneal hematoma. Selective embolization (not shown) was promptly performed because of lowering blood pressure. (D) Contrast-enhanced follow-up CT image at 12 months shows the zone of ablation with no evidence of residual disease.
Copyright Kamran Ahrar, MD
(A) Axial CT image of the kidney during cryoablation of a left upper pole tumor shows proximity of the growing iceball ( arrows ) to the colon ( asterisk ). (B) Hydrodissection was performed by injection of 180 mL of sterile fluid with a small amount of iodinated contrast to separate the colon from the iceball.
Copyright Kamran Ahrar, MD.
The basic principles of ablation are discussed elsewhere in this volume. In this chapter, we briefly discuss specific ablation devices that are commonly used to treat RCC. Our main focus is a review of indications, contraindications, technique, complications, follow-up care, and outcomes of percutaneous ablation of RCC.
Ablation Devices
Radiofrequency Ablation
Currently, three RFA devices have been approved by the US Food and Drug Administration and are commercially available in the United States. Each of these devices uses a generator to deliver alternating electrical current via an electrode, causing ionic agitation and frictional heating within the target tissue. Each of these ablation systems uses a different strategy to obtain the largest possible zone of ablation. The maximum attainable in vivo ablation zone varies by applicator size and design and is consistently less than the ex vivo maximum, in part owing to the presence of adjacent flowing blood or large fluid-filled structures that produce a cooling or heat-sink effect.
Radiofrequency applicators range in size from 17 to 14 gauge and vary in design. Some electrodes are multitined applicators with an expandable array design that allows for a scalable teardrop-shaped or spherical ablation zone. Another system uses a straight probe design with a central channel that allows for circulation of chilled fluid as the basis for an internally cooled electrode. The cooling of the electrode tip and the pulsed delivery of energy help prevent charring of the tissue or excess gas formation. This strategy is expected to maximize the potential zone of ablation.
Cryoablation
The two cryoablation systems currently available in the United States for percutaneous image-guided ablation are the SeedNet System (Galil Medical, Arden Hills, MN) and Endocare (Endocare, Inc., Austin, TX). In both systems, highly compressed argon gas is allowed to expand in a Joules-Thompson chamber in the distal end of the cryoprobe, resulting in intense cooling, which creates an iceball within the target tissue. Helium is used in a similar fashion to actively thaw the iceball. Cryoprobes used in percutaneous ablation range in size from 17 gauge to 2.4 mm in diameter. The critical temperature required to achieve tissue necrosis is −19.4°C in normal renal tissue and −40°C in cancer cells. This temperature must be transmitted throughout the entire tumor. There is a rapid drop in temperature at the edge of the iceball; thus, to achieve the required temperature for cell death throughout the entire tumor, the iceball must extend for at least 3.1 mm beyond the tumor margin.
Microwave Ablation
MWA has gained wide acceptance as a thermal ablative technique. Various MWA systems have been approved for clinical practice in the United States: Certus 140 percutaneous microwave device (NeuWave, Madison, WI), pMTA (percutaneous Microwave Tissue Ablation) System (Acculis, Hampshire, UK), Microwave Ablation System (Valley Lab/Covidien, Boulder, CO), MedWave (San Diego, CA), Amica (Rome, Italy), and the MicroThermX (BSD Medical, Salt Lake City, UT) MWA systems.
During MWA, energy is induced through the delivery of electromagnetic waves into the microwave probe (antenna). This results in energy transmission to the target tissue surrounding the probe with subsequent molecular agitation, friction, and rise in the temperature, thereby inducing cell death and coagulative necrosis. MWA has shown several advantages over RFA including superior thermal efficacy leading to larger ablation zones, less heat-sink effect, increased efficiency in coagulating blood vessels, and shorter ablation time.
Irreversible Electroporation
Irreversible electroporation (NanoKnife, AngioDynamics, Latham, NY) is a relatively novel ablative technique. The ablation is predominantly nonthermal and is mostly electric, based on the electroporation phenomenon. Application of ultrashort pulses (microseconds) of direct electric current into the cells create nanopores in the cell membrane (reversible electroporation), which if became permanent (irreversible electroporation), would lead to disruption in the hemostatic mechanisms of the cells resulting in cellular death. Some researchers have evaluated this novel technique in different organs (e.g., liver, prostate, lung, and kidney). Several alluring characteristics of IRE ablations have been reported, making this novel technique an attractive option for ablating tumors in close proximity to vital structures or heat-sensitive areas. Currently, the clinical data available on the use of IRE for renal tumors is very limited.
You're Reading a Preview
Become a Clinical Tree membership for Full access and enjoy Unlimited articles
If you are a member. Log in here