Hepatic Ablation: Hepatocellular Carcinoma and Metastases
Hepatocellular carcinoma is the fi fth most common cause of cancer in the world and its incidence is increasing worldwide because of the dissemination of Hepatitis B and C infection [ 1–6 ]. Approximately 5–15% of cirrhotic patients with hepatocellular carcinoma meet the criteria for surgical resection [ 5, 7–11 ]. Patients with cirrhosis are at the highest risk of developing hepatocellular carcinoma and should be monitored with imaging every 6 months [ 12 ]. The mortality of patients with hepatocellular carcinoma that is not treated is essentially 100%. The liver is the primary and solitary site of metastatic disease in many malignancies including colorectal cancer, neuroendocrine malignancies, and ocular melanoma with approximately 50,000 cases of hepatic metastases from 145,000 new cases of colorectal cancer diagnosed each year [ 13, 14 ]. Unfortunately, because most hepatic metastases are in unresectable locations or in patients with poor hepatic reserve, curative resection is only possible in 20% of patients at the time of presentation in the case of metastatic colorectal carcinoma[15–19].
Hepatocellular carcinoma is the fifth most common cause of cancer in the world with increasing incidence and high mortality rate if left untreated.
The liver is the primary and solitary site of metastatic disease in many malignancies, most commonly colorectal carcinoma.
Fewer than 20% of cases of patients with metastatic colorectal cancer and hepatocellular carcinoma are candidates for surgical therapy.
Hepatic ablative techniques have the best outcomes when targeted tumors are 3 cm or smaller.
Contraindications to percutaneous ablation include: patients with significant extrahepatic disease, Childs class C cirrhosis, active infection, lesions that are inaccessible, tumors that occupy greater than 30% of the liver volume, and tumor proximity of less than 1–2 cm to the main bile ducts.
The use of preprocedure antibiotics should be reserved for patients with increased risk of developing hepatic abscess postprocedure, such as bacterial colonization of the biliary system and diabetes mellitus.
An appropriate plan to access the lesion should be determined to avoid damage to other structures. Percutaneous injection of CO2, dextrose solution, and/or balloon interposition can be used to dissect away adjacent structures and maintain an adequate margin around the ablation probe.
Most radiofrequency ablation electrodes create an ablation zone of 3 cm, allowing for treatment of a lesion that is 2 cm in diameter with a 5 mm margin. Multiple overlapping ablations or electrodes are needed to treat larger lesions.
The goal temperature for RFA is 50–100 C.
Most patients will develop a postablation syndrome consisting of low-grade fever, and muscle aches that should be managed supportively.
Long-term follow-up after hepatic ablation should be performed with multiphase CT or MRI immediately following treatment as well as 1 and 3 months postprocedure. Once disease control is documented, subsequent follow-up imaging should be performed at 3-month intervals utilizing the same imaging modality for ease of comparison.
PET scanning and laboratory tumor markers may also be a useful tool to assess for residual or recurrent tumor.
Microwave ablation is useful for ablation near major hepatic vessels due to the lack of the “heat sink” effect with one study reporting no significant difference between MWA and RFA.
PEI has higher rates of local tumor progression at the ablation site than RFA. Survival data favors RFA.
Local control of metastatic disease to the liver such as colorectal carcinoma can be achieved in up to 78% of patients with radiofrequency ablation. Outcomes are best with smaller tumors (<3 cm).
Survival in patients with metastatic disease is better for patients who are able to undergo surgical resection rather than percutaneous RF ablation.
Percutaneous ablation can be used for local tumor control in metastatic disease as well as symptomatic relief for patients with metastatic neuroendocrine carcinoma or pain from tumors stretching the hepatic capsule.
Major complications occur in 0.9–5.7% of patients and include intraperitoneal bleeding, liver abscess, intestinal perforation, pneumothorax/hemothorax, bile duct injury, and seeding of the tract by tumor.
The mortality rate from hepatic RF ablation is 0.1–0.5%.
Minor complications or side effects include periprocedural pain, fever, asymptomatic pleural effusion, and grounding pad burns with an overall rate of minor complications ranging from 1.7% to 6.3%.
KeywordsBile Duct Injury Ablation Zone Percutaneous Ethanol Injection Microwave Ablation Left Hepatic Lobe
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