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22 Embolization of Benign and Malignant Renal Tumors 219
Angiography
Flush aortography can be helpful in patients with large tumors when the blood
supply may not derive exclusively from the renal artery.
• Either perform initial flush aortogram to obtain an overview and identify the
position of the renal arteries before embolization.
• Or reserve flush aortography for after-embolization of the main renal artery to
identify alternative tumor supply.
• If in doubt, perform selective angiography of all potential vessels of supply.
• Pre-nephrectomy angiography is solely intended to demonstrate the entire tumor
and renal supply and its subsequent occlusion.
Assessing the Lesion
Location: the location of the tumor should be known from the pre-operative
imaging.
Angiographic Appearance
• The tumor is identified by chaotic neovascularization replacing the typical
branching pattern of the normal renal artery.
• Look for aneurysms and vascular displacement in AML.
Treatment Plan and Technique
The treatment plan and embolic agent depend on the indication.
Pre-operative Embolization
• Goal is to prevent venous bleeding from extensive collaterals and in patients
with extensive renal vein or IVC tumor involvement embolization can lead to
marked retraction of the “tumor thrombus” thus reducing the need for caval/atrial
clamping and cardiopulmonary bypass.
• Performed immediately before surgery if possible. This minimizes post-
embolization syndrome and complications due to local inflammation.
• Main renal artery.
• Use gelfoam/particles to slow the flow before occluding the main renal artery.
Note a guiding catheter allows gelfoam to be injected very readily but has a
220 D.O. Kessel
large dead space with high potential for non-target embolization if flushed. Either
remove the hemostatic valve and aspirate or remove the catheter and flush.
• AVP is ideal to occlude the main renal artery especially when hypertrophied.
• Coils or AVP are deployed close to the bifurcation of the renal artery rather than
at the origin of the vessel as this allows the surgeon to clamp and ligate the
artery.
• Embolization is complete when the vast majority of tumor flow has been
obliterated—remember that you are trying to make the surgery simpler with less
bleeding from collateral veins.
• Leave any tumor supply arising from the mesenteric vessels. You will cause more
harm than good.
• Inform the surgeon what you have done, especially if significant supply
persists.
Embolization in Patients with Inoperable Cancer
• Aim to devascularize the tumor alone in order to relieve symptoms.
• May be performed selectively if desire to preserve renal function equivalent to
partial nephrectomy.
• Permanent agent such as PVA should be used to occlude the tumor circulation.
• Alternative agents: 50:50 mixture of alcohol/lipiodol, Glue or Ethibloc. Liquid
agents are most often given through an occlusion balloon to prevent reflux.
• The inflow vessel is spared to allow access in future if needed.
Embolization in AML
• Goal is permanent embolization of AML with preservation of normal renal tissue.
• Performed as selectively as possible.
• Occlude tumor circulation with permanent agent, e.g., PVA. Alternative agents:
50:50 mixture of alcohol/lipiodol, Glue or Ethibloc.
• Coils should be used to occlude the inflow as there is a risk of post-embolization
aneurysm rupture.
• Look for additional supply to the tumor after the principal supply has been
treated.
• AML should be treated as part tumor and part aneurysm; hence it is necessary to
occlude both the tumor circulation and the arterial inflow.
Arterial Puncture Site
• Use a closure device if patient is in pain or agitated as less likely to lie still.
• It is essential in patients who are going to the operating theatre, as the groin will
not be observed during surgery.
22 Embolization of Benign and Malignant Renal Tumors 221
Post-embolization Syndrome
• Ensure that the patient is prepared for this and knows that pain and sickness can
be treated effectively.
• Treatment is supportive.
• Ensure that the ward staff know what to look for and do.
Follow-Up
• Embolotherapy is usually effective in all of the above situations.
• Patients require follow-up imaging if symptoms recur.
• Following embolization of large AML, it is helpful to demonstrate tumor
devascularization and shrinkage.
• Patients with multifocal AML are managed expectantly and only treated when
symptomatic as the loss of renal tissue would otherwise be too great.
Alternative Therapies
The indications for embolization are well established and should be offered
according to local expertise.
Specific Complications
Renal failure should be managed by a renal physician.
Keypoints
Review the pre-procedural imaging to plan the procedure.
Ensure you understand the rationale for treating each patient; this will ensure
the following:
• Correct choice of embolic agent
• Correct endpoints
• Appropriate consent
Consider the possibility of extensive arterial supply to renal cancers.
Ensure adequate supportive therapy before, during, and after the procedure.
Perform pre-operative embolization as close to surgery as is practicable.
222 D.O. Kessel
Safety
Never start embolization until you have personally reviewed the imaging.
Stick to the indications for the procedure, use appropriate agents, and
remember the endpoints depend on the indication.
Stop if uncertain, especially if there is risk of non-target embolization.
Suggested Reading
Kothary N, Soulen M, Clark T, Wein A, Shlansky-Goldberg R, Crino P, Stavropoulos W.
Renal angiomyolipoma: long-term results after arterial embolization. J Vasc Interv Radiol
2005;16:45–50
Rimon U, Duvdevani, Garniek A, Golan G, Bensaid P, Ramon J, Morag B. Large renal angiomy-
olipomas: digital subtraction angiographic grading and presentation with bleeding. Clin Rad
2006;61(6):520–526
Chapter 23
Embolization of Bone Tumors
Eric J. Hohenwalter, William S. Rilling, and David M. King
Clinical Features
• Bone tumor embolizations can be performed for palliation of pain/symptoms, or
pre-operatively to reduce blood loss during surgery.
• Embolization has been described as definitive treatment for aneurysmal bone
cyst, osteosarcoma, and giant cell tumors refractory to conventional treatment.
• The most common hypervascular metastatic bone tumors include hepatocellular
carcinoma, renal cell carcinoma, thyroid carcinoma, neuroendocrine malignancies, multiple myeloma, lung cancer, leiomyosarcoma, and angiosarcoma.
• Typically performed in conjunction with an orthopedic surgeon or musculoskele-
tal oncologist in order to optimize care.
Diagnostic Evaluation
Laboratory
Evaluate renal function prior to embolization procedure. Ensure adequate hydration
pre- and post-procedure.
Imaging (Fig. 23.1)
Use contrast-enhanced computed tomography (CT) or magnetic resonance imaging
(MRI) for the following
• To demonstrate location of tumor and to evaluate for any satellite lesions.
• To assess tumor vascularity and surrounding anatomy.
• Dedicated CT or MR angiography may demonstrate feeding vessels.
• To form treatment plan and approach.
Transcatheter Embolization and Therapy,
Techniques in Interventional Radiology, DOI 10.1007/978-1-84800-897-7_23,
C
Springer-Verlag London Limited 2010
223
224 E.J. Hohenwalter et al.
a
Fig. 23.1 Pre-procedure imaging. (a and b) Coronal and axial MR with contrast demonstrating a
hypervascular mass in the proximal humerus
b
Indications
• Facilitation of subsequent surgical excision/spinal stabilization
• Symptomatic relief from painful bone metastasis
• Inhibition of tumor growth
• Control of hemorrhage
Alternative Therapies
• Cementoplasty
• Radiofrequency ablation
Contraindications (Relative)
• Renal insufficiency
• Patient unable to be positioned for embolization procedure
• Massive arteriovenous shunting (rare)
• Severe contrast allergy
• Uncorrectable coagulopathy
Specific Complications
• These relate to the vascular territory from which the tumor supply arises.
• Damage to the spinal cord is the most feared complication.
23 Embolization of Bone Tumors 225
Anatomy
• Assess vascularity of the tumor on pre-procedural imaging. Vascular anatomy
will vary depending on location of tumor.
• Evaluate for associated soft tissue mass.
• Evaluate extent and potential involvement of adjacent structures.
• Must assess proximity to significant vessels, such as the s pinal artery in cases of
vertebral metastases.
Equipment
Catheters
• Non-selective catheters: Pigtail or flush catheter for arterial mapping.
• Selective catheters: cobra, angled catheter, or guide catheter.
• Microcatheters: high-flow microcatheters allow for power injection and improved
angiographic visualization, as well as less clumping of embolic agents.
Embolic Agents
• PVA or Embospheres (Biosphere Medical, Rockland, MA, USA): usually 300–
500 μm, but particle size depends on size of artery and A-V shunting.
• Gelfoam (Upjohn, Kalamazoo, MI, USA).
• Microcoils—especially for coil protection of non-target branches.
• Liquid embolic agents.
Medication
Bone tumor embolization can be painful and induces post-embolization syndrome.
• Post-operative pain control: patient-controlled analgesia and anti-inflammatory
medications as needed.
• Infection control: pre-procedure antibiotics (usually Cefazolin or Clindamycin).
• Hydration: intravenous normal saline.
• Post-embolization syndrome: supportive therapy. Anti-emetics, anti-inflamma-
tory, and oral pain medications as needed.
Procedure
Access
• Plan according to pre-procedure imaging.
• Vast majority will be common femoral artery approach.
226 E.J. Hohenwalter et al.
Angiography
• Initial flush arteriogram to map out arterial anatomy. For spinal and pelvic
tumors, an aortagram is performed initially. For peripheral tumors, an arteriogram
of the main extremity artery is performed.
• Selective arteriogram. In tumors of the spine, this must include visualization of
the arteries at levels above and below the tumor.
• When stable selective catheter position is achieved, a microcatheter is usually
used to select the arteries directly supplying the tumor.
• Evaluate for significant non-target branches and consider coil protection depend-
ing on size and distribution of vessels.
• Non-selective arteriography post-embolization to assess for residual tumor blush,
collateral arterial feeders, and adequacy of embolization.
• Frequent control angiography as pressure/flow relationships change during
embolization. This may increase the risk of non-target embolization.
Assessing the Lesion
Location: determined from pre-operative imaging.
Angiographic Appearance
• Evaluate number and origin of tumor feeding vessels.
• Identify arteriovenous shunts.
• Evaluate for collateralization to or from adjacent healthy tissue especially spinal
supply.
Treatment Plan and Technique
The treatment plan and embolic agent depend on the indication.
Pre-operative Embolization (Fig. 23.2)
• The goal is to exclude all of the capillary bed in order to prevent excessive blood
loss at surgery. Lack of tumor blush is the angiographic endpoint; however, any
decrease in flow is helpful to the surgeon.
• Should be performed within 24 h of surgery. This prevents significant collateral
vessels from forming between the embolization and surgery.
• Generally use small (100–200 μm) or medium (300–500 μm) particles or
Gelfoam slurry.
• For larger tumors of the spine, it may be necessary to coil-embolize the feed-
ing artery distal to the target, prior to subselective embolization. This will help
prevent non-target embolization of the adjacent tissues as well as prevent any
retrograde filling of the tumor.
23 Embolization of Bone Tumors 227
a
c
b
d
Fig. 23.2 Pre-operative embolization with coil protection. (a and b) LUE arteriogram demon-
strating a hypervascular mass in the proximal L. Humerus and associated pathologic fracture. (c)
Selective arteriogram through a high-flow microcatheter after coil protection of arteries supplying
normal tissue. (d) Post-particle embolization demonstrating a significant decrease in tumor blush
Palliative Embolization
• The goal is to inhibit tumor growth or decrease the size of the tumor, resulting in
a reduction in tumor-associated pain.
• Particles are the embolic agent of choice. Size depends on the size of the feeding
artery (typically 300–500 μm).
• Some studies have reported increased effectiveness when a chemotherapeutic
agent (most frequently carboplatin) is mixed with the particles.
• The combination of embolization with radiation therapy may further increase the
efficacy of palliative embolization.
228 E.J. Hohenwalter et al.
Embolization as a Primary Treatment
• Most frequently used in aneurysmal bone cysts and giant cell tumors.
• Advantageous in treatment of tumors of the spine and long bones, so as to avoid
radical excision and rigid fixation.
• Treatment goal is to exclude capillary bed.
• Particle embolization is the agent of choice, with sizing according to vessel
diameter.
Complications
• Non-target embolization
• Renal failure
Post-embolization Syndrome
• Treatment is supportive (intravenous fluids, anti-inflammatory medications, anti-
emetics).
• Ensure the patient and nursing staff are aware of post-embolization syndrome,
and know what to expect.
Follow-Up
• Should be done in conjunction with a musculoskeletal oncologist/surgeon.
Keypoints
1. Use pre-operative imaging to guide embolization.
2. Base embolic agent choice on indication and size of feeding artery.
3. Always be aware of the potential for non-target embolization (coil
protection may be necessary).
4. Perform pre-operative embolization as close to surgery as possible.
5. Ensure adequate pre- and post-procedure supportive care.
6. Consult with a musculoskeletal oncologist/surgeon regarding specific
treatment goals and follow-up.