Regional and local ablative methods for treating tumors are expanding the therapeutic role of interventional radiologists. Specifically, intra-arterial chemoembolization and direct tumor ablation with chemicals or thermal devices play an important part in the therapy of many oncologic patients. As these techniques become further developed, the interventional radiologist increasingly will be called upon to assist in the management of tumors, adding to the surgical, systemic chemotherapeutic, and radiation options currently available. This article presents a review of the most common regional and local ablative techniques for treating hepatic lesions and briefly discusses the treatment of other tumors, including those involving the bones and kidneys.
Dr. Hanson has just completed his interventional radiology
fellowship at the Hospital of the University of Pennsylvania in
Philadelphia, PA. He received his MD from the University of
Iowa in Iowa City in 1995 and completed his diagnostic
radiology residency at the University of Utah in Salt Lake City
in 2000. Dr. Hanson will be joining Medical X-Ray Consultants
in Eau Claire, WI, in July 2001.
Dr. Michael Soulen is an Associate Professor of Radiology
and Surgery at the Hospital of the University of Pennsylvania,
Philadelphia, PA. He has a special interest in
chemoembolization and other loco-regional cancer
A variety of ablative techniques have been developed to
complement the traditional surgical and oncologic approaches used
in treating tumors. These techniques include transarterial
chemoembolization, percutaneous ablation with chemicals such as
alcohol or acetic acid, or percutaneous treatment with
radiofrequency ablation or cryotherapy. The clinical management of
primary and metastatic hepatic tumors can be especially
challenging. Therefore, regional and local ablative techniques used
in the treatment of hepatic tumors have been studied extensively.
More recently, these techniques have been used in treating a
variety of other tumors, including renal and osseous tumors.
Hepatocellular carcinoma (HCC) has a worldwide annual incidence
of more than 1 million people, making it one of the most common
fatal malignancies. Colorectal carcinoma is the third leading cause
of death due to cancer in the United States and is frequently
metastatic to the liver. Surgical excision is the ideal treatment
for these tumors, but only 5% to 15% of patients are candidates,
and the 5-year survival is 20% to 40%.
Systemic chemotherapy and external beam radiation therapy have
limitations due to poor tumor response and hepatic toxicity.
Regional and local ablative techniques continue to be refined in an
attempt to achieve better outcomes for the large number of patients
who are not operative candidates.
Regional ablation of hepatic malignancies
The intra-arterial administration of chemotherapeutic and
embolic agents has many potential advantages, including increased
concentration and dwell time of the chemotherapeutic agents within
the liver, decreased systemic toxicity, the development of tumor
ischemia, and ischemia-induced failure of cell membrane pumps
leading to increased intracellular drug levels.
--Candidates for chemoembolization must have their tumor confined
to the liver, or the tumor must be liver-dominant and a significant
source of morbidity and mortality. This generally includes patients
with HCC and liver metastases from colorectal carcinoma, ocular
melanoma, islet cell tumors, carcinoid tumor, and sarcomas.
Occasionally, patients with liver metastases from other sites also
are candidates. Assessment of portal venous flow is necessary, and
if it is diminished the presence of collateral hepatopedal flow
must be demonstrated.
Poor hepatopedal flow may necessitate more selective
chemoembolization. Biliary obstruction increases the risk of
biliary necrosis. Jaundice and hepatic encephalopathy are absolute
contraindications. Patients with >50% liver volume replaced by
tumor, lactate dehydrogenase (LDH) >425 IU/L, aspartate
aminotransferase (AST) >100 IU/L, and total bilirubin >= 2
mg/dL are at increased risk for acute hepatic failure.
The procedure for chemoembolization at the University of
Pennsylvania has been well described.
Three chemotherapeutic drugs are dissolved in contrast and
emulsified with iodized oil. Polyvinyl alcohol (PVA) particles
measuring 150 to 250 µm are added toward the end of the procedure.
Embolization is performed until there is peripheral arterial
pruning but not complete stasis of flow (figure 1). Standard orders
for patients are listed in figure 2. Some institutions use
different chemotherapeutic and embolic agents. Some institutions do
not use iodized oil. The potential advantages of iodized oil
include its drug-carrying ability, tumor-seeking ability, and
However, the dose of iodized oil should be <0.2 mg/kg to avoid
liver and pulmonary toxicity. The final angiographic images help
determine the need for repeat treatment, which usually is performed
at 3- to 4-week intervals. Typically, 2 to 4 treatments are
performed in a lobar or segmental distribution. Response is
assessed using tumor markers and cross-sectional imaging.
Distinguishing residual or recurrent disease from anatomic changes
caused by the ablative procedure itself can be challenging. Murphy
proposed a window/level setting of 110/75 Hounsfield units to
improve lesion detection on post-chemoembolization computed
tomography (CT). Iman et al
used diffusion-weighted magnetic resonance imaging (MRI) to
evaluate tumor necrosis post-chemoembolization and have found it
especially useful with HCC. Fluoro-deoxyglucose-positron emission
tomography (FDG-PET) has been found to be more accurate than CT in
evaluating the efficacy of chemoembolization of HCC and colorectal
Major complications occur in 3% to 4% of cases and include hepatic
insufficiency or infarction, hepatic abscess, tumor rupture,
surgical cholecystitis, and nontarget embolization. Geschwind et al
describe no significant deterioration in liver function following
chemoembolization in 33 patients with Childs class A and 22
patients with Childs class B. The formation of liver abscesses has
been associated with prior bilioenteric anastomosis despite
standard antibiotic prophylaxis (figure 3). Liver abscesses
occurred in 7 of 157 patients (8 of 397 procedures) with 6 of these
patients having had a prior Whipple procedure.
Additional antibiotic prophylaxis and bowel preparation may be of
benefit in this patient group.
--For HCC treated palliatively in a combined series of 800 patients
from the United States, Europe, and Asia there was a 60% to 83%
response rate characterized by decreasing serum alpha-fetoprotein
and tumor volume. Probability of survival was 54% to 88%, 33% to
64%, and 18% to 51% at 1, 2, and 3 years, respectively.
A European multicenter trial of 100 patients (90% Stage I) showed
survival rates of 62% and 38% at 1 and 2 years compared with
survivals in nontreated patients of 43% and 26%.
A French multicenter trial showed similar results in more advanced
disease (62% Stage II or III) with treated survival of 64% and 38%
compared with nontreated survival of 18% and 6% at 1 and 2 years,
Prognostic factors include tumor size and type, staging, Childs
class, and the degree of oil uptake by the tumor.
Uraki et al
reported a 23-month mean survival for patients with nodular-type
HCC (11 patients) compared with a 10-month mean survival for
patients with diffuse-type HCC (39 patients). Portal vein invasion
was not found to be a significant prognostic factor. Balzano et al
have shown a 100% 12-month survival (43% at 2 years, 29% at 3
years) in 7 patients receiving chemoembolization (cisplatin and
gelfoam) for recurrent HCC following liver transplantation.
Patients received 4 to 12 cycles of chemoembolization repeated
every 6 to 8 weeks.
Several Phase II studies have been performed for metastatic
colorectal carcinoma demonstrating a 60% to 70% response rate and a
2-year median survival.
The American College of Radiology Imaging Network (ACRIN) is
funding a randomized multicenter trial of systemic chemotherapy,
with or without chemoembolization, to prospectively evaluate the
survival benefit of chemoembolization for metastatic colon
With traditional therapy, median survival of metastatic ocular
melanoma is 2 to 6 months. Median survival for 30 patients treated
with chemoembolization for ocular melanoma (cisplatin and polyvinyl
alcohol particles) at M.D. Anderson Cancer center was 11 months.
Mean survival for 28 patients treated with chemoembolization for
ocular melanoma (BCNU [Carmustine, Bristol-Myers Squibb
Oncology/Immunology Division, Princeton, NJ], Ethiodol [Savage
Laboratories, Melville, NY], and gelatin sponge) at Thomas
Jefferson University Hospital was 208 days (range 4 to 82 days).
Tumor burden significantly influenced survival. Patients having
<20%, 20% to 50%, and >50% liver replacement by tumor
survived a mean of 471, 199, 107 days, respectively (
Chemoembolization of hepatic metastases from breast carcinoma has
been shown to decrease or stabilize the hepatic tumor burden in 7
of 8 patients treated at the University of Pennsylvania with the
potential to palliate symptoms. However, mean survival following
the first embolization is only 6 months due to development or
progression of extrahepatic metastatic disease.
Results in neuroendocrine tumors--
Bland embolization of neuroendocrine tumors, especially carcinoid
tumors, can lead to cessation of symptoms for 5 to 10 months in 90%
to 100% of patients. Chemoembolization can increase the cessation
of symptoms to nearly 2 years, but there is a concern for increased
complications compared with bland embolization.
The release of vasoactive factors can lead to hypertensive crises
as well as hypotension. Nowakowski et al
retrospectively evaluated 159 hepatic chemoembolization procedures
in 80 patients with metastatic carcinoid tumor. Hypertensive or
hypotensive events occurred in 4.4% of cases and were all
controlled periprocedurally. Patients were premedicated with
octreotide (100 to 500 mg every 8 hours), hydrocortisone (100 mg
every 6 hours), and ondansetron. An anesthesiologist administered
conscious sedation. There was 1 periprocedural death due to
hepatorenal syndrome, but no deaths were reported due to the
release of vasoactive factors. At the University of Pennsylvania,
24 patients were treated for hepatic metastases of neuroendocrine
tumors with a major complication rate of 6.4% and 1 patient death
due to liver failure. There was morphologic tumor regression in all
19 patients for whom follow-up imaging was available. Survival was
roughly estimated in this small sample size as 71% and 58% at 1 and
2 years, respectively.
The treatment of HCC with doxorubicin hydrochloride adsorbed to
magnetic targeted carriers is being evaluated by Goodwin et al
at UCLA. An external magnet positioned over the tumor was activated
during infusion of the agent into the hepatic artery. Patients were
evaluated with MRI immediately following the procedure to assess
the location of the magnetic targeted carriers. Tumor size was
evaluated with CT at baseline and at 28 days. Targeting of the
agent within the tumor was achieved in 19 of the 21 patients. No
drug was detected in the systemic circulation. Preliminary data in
10 patients showed tumor progression in only 1 patient,
stabilization in 5 patients, and minor or partial responses in 4
patients. Dosing of the agent based on size of the tumor is being
investigated. Coldwell et al
are evaluating the treatment of primary and secondary hepatic
tumors using intra-arterial embolization with Yttrium-90 glass
microspheres. Patients received an average radiation dose of 146
Gray. Complications reported in 13 patients include 1 case of
intrabdominal hemorrhage and 1 case of stroke 3 days following
embolization. Additional outcomes have yet to be reported.
Percutaneous ablation of hepatic malignancies
Ablation of hepatic malignancies using a direct percutaneous
approach involves chemical and thermal techniques. Chemical
ablation includes absolute alcohol or acetic acid injection, and
thermal techniques consist of radiofrequency, cryo-, microwave,
laser, or high-intensity ultrasound ablation. Chemical ablation
causes coagulative necrosis due to cytoplasmic dehydration,
denaturation of cellular proteins, and small vessel thrombosis.
Thermal ablation creates a focal area of tissue coagulation
dependent on the local temperature produced by the specific
Patients with unresectable, small, intrahepatic tumors that can
be localized with ultrasound or CT imaging are the best candidates
for direct percutaneous techniques. Patients with resectable tumors
who are poor operative candidates may also be considered. Patients
with tumors >3 cm in size or >3 in number have a poorer
response to these techniques.
Percutaneous ethanol injection
Percutaneous ethanol injection (PEI) has been shown to be safe,
effective, and inexpensive in treating small (<3 cm), unifocal
The procedure for PEI involves conscious sedation and can be done
on an outpatient basis. Using sterile technique, following local
anesthesia with Lidocaine, a 20-gauge needle (for example, a
diamond tip, multi-sidehole Bernadino needle) is advanced under
ultrasound or CT guidance to the far wall of the tumor and then
slowly withdrawn as the ethanol is injected. Injection is
discontinued if flow into adjacent structures is noted. Ethanol is
brightly echogenic on ultrasound, likely due to microbubbles
injected with the ethanol. Ethanol is hypodense on CT. The needle
is left in place for 1 to 2 minutes and then withdrawn while
aspirating. The total volume is calculated using the radius of the
tumor and the formula for the volume of a sphere (4/3¼ [r+0.5]
). The addition of 0.5 cm to the radius allows for a "tumor-free"
margin. A 3-cm lesion therefore requires a total volume of 33 mL
(Table 1). Lesions >4 cm usually require additional sessions due
to alcohol toxicity (1 mL/kg). Follow-up evaluation is performed
with CT, MRI, or PET and tumor markers.
Pain and nausea during the procedure as well as fever and elevated
liver enzymes in the subsequent few days are not uncommon. More
significant complications occur in 1% to 4% of patients.
Complete necrosis occurs in 60% to 80% of patients, but 64% to 98%
of patients develop new tumors in 5 years with a 5-year survival of
30% to 50%.
Patients with Childs class C have not demonstrated improved
Use of ethanol following chemoembolization can improve ethanol
diffusion. One study showed patients with tumors 3 to 8 cm in size
having improved survival with ethanol following chemoembolization
versus chemoembolization alone.
However, there are disadvantages to PEI. Multiple sessions are
usually required, and treatment of multifocal disease is limited.
PEI is less effective in treating metastatic disease, such as
colorectal carcinoma, due to limited diffusion through this
relatively firm tumor.
Because of these limitations, PEI is being replaced by other
techniques in many centers.
Acetic acid ablation
Acetic acid has been shown by Ohnishi et al
to have superior cell kill at lower volumes compared with ethanol.
Acetic acid has a higher degree of necrosis, more homogeneous
diffusion, and is able to infiltrate tumor septae and capsules
Acetic acid is administered in a similar fashion to ethanol.
Because of the increased diffusion, the dose is reduced by 1/3
compared with ethanol (Table 1) and the injection is performed very
slowly. An injection >20 mL has the potential risk of renal
toxicity and metabolic acidosis. As with alcohol, multiple sessions
can be performed if necessary.
In a prospective randomized trial, Ohnishi et al
demonstrated a need for fewer treatment sessions and decreased
volume with injections of acetic acid (31 patients) compared with
ethanol (29 patients) for treatment of small, HCC (<3 cm).
Cancer-free survival at 1 and 2 years was 83% and 63% with acetic
acid, compared with 59% and 33% with ethanol. There were no major
complications. Liang et al
treated 22 HCC nodules with a single acetic acid injection.
Seventeen of 21 nodules evaluated on follow-up CT (at 6 to 29
months) showed complete necrosis. Injection was terminated
prematurely in the other four nodules due to pain or intravasation
of acetic acid. Three of these nodules showed complete necrosis
following a second injection. Recently, acetic acid has been shown
in vivo to produce significantly increased parenchymal diffusion
and larger zones of necrosis in porcine liver.
The diffusion characteristics of acetic acid may make it a useful
agent in treating metastatic disease to the liver.
The use of radiofrequency ablation (RFA) for treating hepatic
neoplasms has received much attention. The devices used in RFA
produce alternating current in the radiofrequency range. This leads
to ionic agitation and frictional heat extending into the tissues
adjacent to the device with subsequent development of coagulative
necrosis. Three radiofrequency devices are available in the United
States (figure 4). The devices have received approval for treatment
of surgically unresectable hepatic neoplasms by the Food and Drug
Administration. Each system has differences in electrode and
generator design. The RITA system (RITA Medical Systems, Mountain
View, CA) uses 4 to 9 retractable needles housed in a 14- or
15-gauge outer needle. Temperature is monitored at the tips of the
electrodes and wattage is adjusted up to a maximum of 150 W to
maintain a target temperature for a set period of time. The
ablation diameter is reported as 3 to 5 cm with the RITA Starburst
XL. The RadioTherapeutics LeVeen Needle Electrode
(RadioTherapeutics Corp., Sunnyvale, CA; distributed by Boston
Scientific Corp., Burlington, MA) has 10 to 12 retractable needles
housed in a 14- to 15-gauge outer needle with a deployed diameter
of 2, 3.5, or 4 cm. A 200-W generator has recently been released.
Instead of using tissue temperature, the device uses an ablation
algorithm based on tissue impedance that increases with tissue
desiccation. An anticipated maximum ablation diameter of 4 cm is
reported by the manufacturer. The Radionics device (Tyco
Healthcare, Burlington, MA) uses a hollow-tip 17-gauge needle as a
single cooled or noncooled electrode or as a Cool-Tip cluster of
three parallel electrodes. Cooling is performed using a saline pump
and is thought to help reduce tissue impedance adjacent to the
electrode tip. The power is supplied by a 200-W generator and is
adjusted according to tissue impedance. Tissue temperature can be
measured with a thermocouple at the electrode tip. A maximum
ablation diameter of 4 to 5 cm is reported.
Radiofrequency ablation can be performed percutaneously,
laparoscopically, or with laparotomy. Evaluation of the number of
tumors and their size is important. Patients with fewer than 5
tumors <5 cm diameter, and with no extrahepatic tumors are good
Tumors numbering fewer than 2 and approaching 5 cm in size become
difficult to fully ablate.
For a device producing approximately a 3-cm ablation, the largest
tumor treated with a single ablation should be 2 cm, allowing for a
tumor-free margin of 5 mm. Most devices produce approximately a
3-cm ablation, so the largest tumor treated with a single ablation
should be 2 cm, allowing for a tumor-free margin of 5 mm. Larger
tumors require overlapping ablations. One method involves creating
overlapping spheres, which yields only 25% more ablation margin
using two spheres in each plane (6 spheres total). Another method
involves creating overlapping cylinders.
Each ablation can last 10 to 30 minutes. Careful preprocedural
evaluation of the tumor is important to assess the best approach,
identify the location of adjacent structures that may increase the
complication risk, and determine the presence of vascular
structures acting as potential heat sinks diminishing the thermal
effect. Patients with Childs class C, active infection, or
uncorrectable coagulopathy are not considered good candidates.
Hepatocellular carcinoma and metastatic colon carcinoma are the
most common neoplasms treated. Metastatic tumors from breast,
pancreas, stomach, and neck as well as neuroendocrine tumors also
have been treated.
The choice of approach is debated in the literature. A percutaneous
approach with ultrasound or CT guidance can be performed on an
outpatient basis with conscious sedation and with minimum morbidity
(figure 5). Laparoscopy allows direct imaging of the liver with a
high-frequency ultrasonic transducer. This improves detection and
visualization of small tumors and affords more accurate staging.
In addition, a Pringle maneuver can be performed (occlusion of the
hepatic artery and portal vein at the porta hepatis during
treatment), which can increase the ablation margins.
However, laparoscopy is more invasive, and the approach is somewhat
limited, depending on the sites chosen for the laparoscopic ports
on the abdominal wall. Laparotomy has advantages similar to
laparoscopy and improves access to the tumor, allowing possible
resection or cryoablation, with the disadvantage of performing an
The RITA and Radionics systems allow cauterization of the
percutaneous tract. A shortened 6F or 7F sheath can be placed on
the RadioTherapeutics electrode prior to insertion and later can be
used for tract embolization using gelfoam pledgets (figure 5). The
RadioTherapeutics system soon will have a coaxial needle electrode
system with an introducer sheath (CoAccess, RadioTherapeutics
Corporation, Sunnyvale, CA) to allow the introduction of a biopsy
gun, gelfoam, or other device.
Follow-up evaluation usually is performed with CT (3-phase for HCC
and 2-phase for colorectal metastases) and tumor markers. Newer
imaging methods, as discussed with chemoembolization, may afford
earlier detection of recurrence or new malignancy.
Increased pain can occur with ablation of tumors near the liver
capsule, gallbladder, main portal vessels, or diaphragm. Ablation
of tumors near the gallbladder can cause cholecystitis. Ablation of
tumors near the portal venous confluence increases the risk of
biliary damage. Thermal necrosis in bowel loops adjacent to treated
subcapsular lesions also can occur. Preventing thermal injury to
the skin adjacent to the grounding pads requires appropriate
placement of the pads on the thighs.
The overall complication rate is <5%.
Complete tumor necrosis rates of 50% to 95% have been reported.
However, rates as low as 25% have been reported for tumors >5 cm
The best local recurrence rate reported is 1.8% for primary and
metastatic tumors following laparotomy and the use of a Pringle
maneuver for 3 minutes.
Recurrence rates are higher with metastatic disease, most likely
due to difficulty in detecting small lesions at the time of
treatment. At the University of Pennsylvania, the cumulative risk
of local recurrence is 15%, and the risk of new lesions is 64% at 1
The use of modified Pringle maneuvers has been studied,
including balloon occlusion of the hepatic artery or gelatin sponge
embolization of hepatic arterial branches. For nodules with
diameters 3.5 to 8.5 cm treated with RFA and a modified Pringle
maneuver, Rossi et al
reported a local recurrence rate of 19%, and an overall
intrahepatic recurrence rate of 45% at 1 year. These results may
reflect preserved portal venous flow to the tumor, preventing
formation of an adequate tumor-free margin. Curley et al
treated 169 hepatic tumors with RFA performed percutaneously (31
patients) or with laparotomy using a Pringle maneuver (92
patients). Median tumor size was 2.4 cm in the patients treated
percutaneously and 3.8 cm in those patients treated surgically.
Local recurrence was 1.8% at 15 months, and 72% of patients were
free of tumor. Wood et al
treated 231 patients with unresectable hepatic tumors with RFA
performed via percutaneous approach (25 patients), laparoscopy (27
patients), or laparotomy (39 patients). Intrahepatic ultrasound
detected additional disease not evident with other imaging in 38%
of cases. Resection and/or cryoablation were used in 38 of 84
patients. Median tumor size was 2 cm. The complication rate was 8%.
Local recurrence was 18% at 9 months, and 43% of patients were free
RFA has been shown to be more efficacious and to require fewer
treatment sessions compared with PEI in treating HCC. Livraghi et
demonstrated a higher rate of complete necrosis in small HCC
treated with RFA (90%) versis PEI (80%). In addition, RFA required
an average of 1.2 treatment sessions per tumor, compared with 4.8
sessions for PEI. RFA had a slightly higher complication rate,
often related to tumor location and heating of adjacent organs. In
these cases, the use of PEI may be more appropriate. As mentioned,
PEI is not useful in treating metastatic disease. RFA has been
shown to be cost-effective compared with palliative care in the
treatment of HCC and metastatic colorectal carcinoma.
Radiofrequency ablation has been used as salvage therapy for
refractory carcinoid metastases with promising results reported in
Other ablation techniques
Cryosurgical ablation has higher morbidity than RFA but still is
used to treat larger unresectable hepatic neoplasms.
In a prospective, nonrandomized trial, Pearson et al
demonstrated a 40.7% complication rate, including 1 postoperative
death, with intraoperative cryoablation compared with a 3.3%
complication rate and no deaths with intraoperative RFA. Tumor
recurrence was 13.6% for cryoablation and 2.2% for RFA at 15
Microwave coagulation therapy and laser photocoagulation are
being used to treat hepatic malignancies in Europe and Japan.
Shibata et al
recently reported that microwave coagulation therapy was as
effective as surgery in the treatment of metastatic colorectal
carcinoma. Thirty patients were randomized to microwave coagulation
therapy or surgery. Mean survival for patients receiving microwave
coagulation therapy during laparotomy was 27 months compared with a
mean survival of 25 months for patients receiving hepatic
resection. (Three-year survival rates were 14% and 23% for
microwave versus surgery,
= nonsignificant.) The average tumor size was 2.7 cm. Complication
rates were not significantly different, but patients receiving
microwave coagulation therapy had decreased blood loss. Microwave
coagulation therapy is most ideal in tumors <2 cm in size. It
has been shown to be effective in HCC in a previous study.
Laser photocoagulation therapy has been described as effective, but
much more interest centers on RFA in this country.
Combination therapy of hepatic malignancies
Accurately ablating the tumor and achieving adequate margins are
crucial. Effective tumor detection also is important. Since
hepatocellular carcinomas are supplied by the hepatic artery, a
combined approach of hepatic arterial occlusion followed by
radiofrequency ablation may prove to be beneficial. Occlusion of
the hepatic artery can be performed with a modified Pringle
maneuver using an occlusion balloon or gelfoam, or a course of
chemoembolization can be administered prior to RFA. Using a Pringle
maneuver during RFA performed during laparoscopy or laparotomy also
has shown potential, as both the hepatic artery and portal vein can
be occluded. As discussed, the latter methods also can have
improved tumor detection in metastatic disease. Ultimately,
combination therapy will have to be modified for each case based on
tumor type, size, and number, as well as patient risk factors. A
team approach to tumor management by oncologists, surgeons, and
radiologists can provide the best care for these difficult
Therapy of other tumors
Chemoembolization or RFA is also being used to treat
malignancies elsewhere in the body.
RFA of both benign and malignant osseous tumors is being
performed. Specifically, RFA is being used to treat osteoid
osteomas. The conventional therapy for these benign, painful tumors
is medical therapy with aspirin or nonsteroidal anti-inflammatory
drugs or surgical or percutaneous resection. RFA of these tumors
offers a less invasive approach and can be performed on an
outpatient basis using CT guidance and general anesthesia or
conscious sedation. Penetration of the cortex with a core bone
biopsy needle and placement of the radiofrequency probe directly
into the nidus are important. Both single and multi-electrode
devices have been used. The procedure has been found to be safe and
effective with pain relief reported in the literature in 83% to 91%
The use of RFA in primary and metastatic malignant tumors alone and
in combination with radiation therapy is also being evaluated at
many centers. There may be a role for RFA in local tumor control
and management of pain.
Intra-arterial embolization of renal angiomyolipomas for the
prevention of hemorrhage is safe and effective.
Angiomyolipomas >= 4 cm are symptomatic in 82% to 94% of cases
and hemorrhage spontaneously in 50% to 60% of cases. A variety of
embolic agents have been used, including absolute alcohol, iodized
oil, particles, and coils. The first two agents have the
theoretical advantage of penetrating to the capillary level,
causing effective tumor necrosis and avoiding repeat therapy due to
the development of collaterals. The disadvantage of ethanol is the
potential for reflux and non-target embolization and thrombosis.
High quality, digital subtraction angiography performed prior to
embolization is important in evaluating for the presence of
aberrant anatomy and possible capsular collateral vessels
communicating with lumbar and mesenteric vessels. An occlusion
balloon can be used to prevent the reflux of ethanol. However, care
must be taken, as aneurysm rupture has been reported as a
complication with this technique. In smaller arteries,
superselective catheters can be used to deliver the combination of
ethanol with iodized oil in a 3:7 ratio (figure 6). Both methods
have been performed at the University of Pennsylvania and have been
found to be 90% effective in 5 patients over a mean follow-up
period of 21 months.
Clinical symptoms disappeared in 13 of 14 patients treated by Han
over a mean follow-up period of 33 months. Han et al
also demonstrated a decrease in the angiomyogenic components of the
tumors on follow-up CT. The treatment of renal cell carcinoma with
radiofrequency ablation is being evaluated. This may prove to be
useful in those patients who are not operative candidates or for
the treatment of small, localized carcinomas.
Coldwell et al
are evaluating the use of intra-arterial platinol in the treatment
of radioresistant head and neck squamous cell carcinomas. A dose of
platinol was delivered every 2 weeks following superselective
arterial catheterization. Follow-up CT was performed. Fourteen
patients received an average of two infusions with complete
response in 7 (50%), partial response in 3 (21%), stabilization in
2 (14%), and progression in 2 (14%). The treatment of desmoid
tumors with percutaneous acetic acid injection is being performed
at the University of Pennsylvania.
The role of the interventional radiologist in oncologic therapy
is expanding. The treatment of hepatic tumors with regional and
local ablative techniques continues to be refined, and similar
techniques are being developed for the treatment of a variety of
other tumors in the body. A combination of the available techniques
most likely will offer the best therapy. The interventional
radiologist has the opportunity to be an important member of the
oncologic team, offering insight and assistance in the management
of a variety of challenging cases. *