Between May 1999 and July 2002, a total of 24 patients with colorectal cancer were treated with RFA for metastatic hepatic tumors at Hanyang University Hospital. Patients underwent a baseline evaluation, including a history, physical exam, CBC, blood chemistry, chest X-ray and CT scans of the abdomen and pelvis. The blood tests were repeated within 7 days of the RFA procedure. A CT scan was initially obtained within 1 day, and then every 3 months up to 2 years. The medical records of these patients were retrospectively reviewed. All patients signed written informed consent.

RFA was performed percutaneously with ultrasound-guidance under local and conscious sedation using lidocaine and demerol, respectively. All RFA procedures were performed by one radiologist (H Rhim). An expandable, 15-gauge, RF electrode (Monoploar 3D & StarBurst; RITA, MountainView, CA) and internally cooled, 18-gauge, RF electrodes (Cool-tip; Radionics, Burlington, MA) were used to apply RF energy to the tumors. The expandable electrodes were used for 18 patients during the early period, while the Cool-tip electrodes were used for 6, as from November 2001. RF ablation was performed with real-time US guidance using free-hand techniques. After cleaning the skin with iodized alcohol, the RF electrode was inserted into the tumor. Grounding was achieved with one or more grounding pads placed on the skin. The target volume for the ablation was defined as the entire tumor, with at least a 0.5 cm ablative margin of apparently normal hepatic tissue surrounding the tumor. For tumors larger than 3 cm in diameter, multiple overlapping ablations were often performed. After ablation, the electrode was removed without cauterization of the tract. Each ablation lasted for 7~15 minutes according to the device and target ablation volume. The mean total procedure time was 60 minutes per session, including tumor localization, treatment, electrode removal and immediate post-procedural US. A dynamic contrast-enhanced CT scan was performed within 12 hours of the procedure to assess the completeness of the ablation and to look for complications. If there was residual tumor on an immediate CT, repeat RF ablation was performed. Additional CT scans were obtained every 3 months after the procedure to look for evidence of residual or recurrent tumors. A systematic review of post therapeutic CT scans was performed to detect not only recurrence of tumor within the liver, but also for an extrahepatic malignancy.

The end points of this study were to evaluate the rates of recurrence and complications of RFA. The time to progression was defined as the time between the date of the RFA and the occurrence of disease progression. Survival was measured from the date of the RFA to the date of death or the last follow-up visit. Survival curves were estimated by the Kaplan-Meier method.

There were 13 male (54.2%) and 11 female (45.8%) patients, with a median age of 63.0 years, ranging from 29 to 77 years. A total of 45 metastatic hepatic tumors, in 24 patients with colorectal cancer, were treated with RFA. RFA was used to treat a single tumor in 11 (45.8%), two tumors in 7 (29.2%), three tumors in 4 (16.7%) and four tumors in 2 patients (8.3%). The median largest diameter of the tumors treated RFA was 3.4 cm (1.7~13.0 cm). 14 and 10 patients had tumors less than and larger than 4 cm, respectively.

All patients had undergone complete or palliative primary tumor resection prior to the initial RFA procedure. Four (16.7%) of the 24 patients underwent resection of liver metastases and 18 (75.0%) received systemic chemotherapy prior to the RFA. Thirteen patients received chemotherapy after the RFA. Eight patients were treated with an oxaliplatin based regimen (the median cycles: 6), two with an irinotecan based regimen and three received 5-fluorouracil.

The RFA results are summarized in Table 1. The rate of complete necrosis was significantly high in patients with tumor less than compared with those larger than 4 cm (p<0.05). The median progression free survival (PFS) and 1-year PFS were 5.5 months and 23.9%, respectively. The achievement of complete tumor necrosis was also an important factor for PFS (median PFS: 7.9 months vs. 3.0 months, p=0.048), but the number of metastasis or size of the tumor was not correlated to the PFS.

The median overall survival (OS) was 17.1 months. The 1- and 2-year survival rates were 80.5 and 25.8%, respectively. In the univariate analysis, complete tumor necrosis, tumor size and post-RFA chemotherapy proved significant factors for survival. The median survival of the patients with complete tumor necrosis was 17.5 months, whereas this was 12.8 months for the incomplete group (p=0.039). The median survival of the patients with tumor less than 4 cm was not reached, compared with the 12.2 months for those with tumors larger than 4 cm (p=0.008, Fig. 1). The patients who received post-RFA chemotherapy also had a significantly longer survival (median OS 20.5 months vs. 12.8 months, Fig. 2). However, the number of metastases did not influence the overall survival.

Twelve of the 24 patients died. The most common cause of death was disease progression, which occurred in 11 patients, and one patient died of complications due to chemotherapy.

Neither death nor serious adverse effects related to RFA were seen. Only 1 patient developed respiratory failure after RFA, but recovered completely with intensive medical care. The serum liver function tests (ALT and AST) were transiently elevated after RFA, but returned to baseline levels in most patients. The serum bilirubin levels rose in 13 patients (54.2%). Fever developed in 3 patients (12.5%), but no cases developed a hepatic abscess (Table 1).