Volumetric Evaluation of Liver Metastases after Thermal Ablation: Long-term Results Following MR-guided Laser-induced Thermotherapy

Abstract

Purpose: To volumetrically analyze liver metastases and posttherapeutic findings of the thermally ablated area after thermal ablation with magnetic resonance (MR)–guided laser-induced thermotherapy in a long-term evaluation using contrast-enhanced MR imaging. Materials and Methods: The study was approved by the institutional review board, and informed consent was obtained from all patients. In 40 patients (27 women, 13 men; age range, 33–94 years; mean age, 62.5 years) in whom colorectal cancer (n = 20) and breast cancer (n = 20) had metastasized to the liver, initial tumor volume and thermal-induced necrosis after MR-guided laser-induced thermotherapy were retrospectively analyzed. All patients presented with oligonodular liver metastases and underwent follow-up with contrast-enhanced MR imaging for at least 3 years. No concomitant oncologic therapies were performed. Results: Volumetric MR imaging evaluation depicted 40 metastases with an initial tumor volume less than 5 mL (x = 1.75), nine metastases with initial volume of 5–20 mL (x = 12.35), and eight metastases with initial volume more than 20 mL (x = 50.57). The mean volume of the thermally damaged area was 498% of the initial volume for colorectal cancer metastases and 604% of the initial volume for breast cancer metastases. The ischemic and necrotic volume for colorectal cancer metastases had decreased by a mean of 48.6% after 3 months, by 63% after 6 months, by 70.2% after 12 months, and by 92.2% after 36 months. For breast cancer metastases at 36 months, the necrotic volume had decreased by 80.61%; the reduction in the volume of the thermally damaged region was statistically significantly lower than that of colorectal cancer metastases. Conclusion: MR-guided laser-induced thermotherapy induced a high volume of thermal ablation; the greatest reduction in the necrotic volume occurred in the first year, and lower values were seen in the next period. The reduction was statistically significantly higher in colorectal cancer metastases. © RSNA, 2008