4.3.4 Local Hyperthermia for Liver Cancer

4.3.4 Local Hyperthermia for Liver Cancer

Local hyperthermia for liver cancer has developed into laser hyperthermia, radiofrequency hyperthermia, microwave coagulation therapy, and focused ultrasound therapy. Laser hyperthermia currently has relatively reliable therapeutic effects; its mechanism involves using ultrasound, CT, or MRI guidance to convert light energy into heat energy, which is absorbed by tumor tissue, raising its temperature and selectively killing cancer cells. Tumor tissue undergoes coagulative necrosis (a range of 0.5–1.0 cm beyond the tumor is ideal), while normal liver cells are rarely damaged. This method is suitable for liver cancers with diameters less than 5 cm and fewer than 3 tumors; laser hyperthermia can destroy them. For tumors larger than 5 cm, fractional hyperthermia or combination with other therapies is required. It is also suitable for elderly patients, those with extrahepatic metastasis, those who cannot tolerate surgery, and those with postoperative recurrence.

Radiofrequency hyperthermia is divided into capacitive heating and thermal ablation. Thermal ablation uses high-frequency alternating current under ultrasound or CT guidance to make the medium in tumor tissue vibrate and rub due to the high-frequency current, generating local high heat that denatures, dissolves, and coagulates cancerous tissue. Capacitive heating places the heat source on the body surface, gradually raising the temperature of the lesion. Although this method is non-invasive, it is difficult to achieve the ideal treatment temperature (41–45°C), so it is often combined with other therapies in clinical practice [88]. Hildebrand et al. [88] observed 88 liver cancer patients and found that after treatment, 83% of tumors were eliminated within 21.2 months, with only a few patients experiencing complications. Microwave ablation therapy utilizes charged ions and polar molecules in microwaves, which undergo polarization vibrations under an alternating electric field. The resulting high heat is absorbed by tumor tissues, which are more thermosensitive than normal tissues, leading to coagulative necrosis of the tumor and achieving the goal of local tumor eradication. Currently, microwave technology has advanced to allow percutaneous puncture and endoscopic treatment; however, due to the limited range of thermal coagulation, this method is suitable for smaller tumors. Liang et al.[90] used microwave ablation therapy to treat 74 patients with liver cancer and found that the 1-year survival rate was 91.4%, the 3-year survival rate was 46.4%, and the 5-year survival rate was 29%, demonstrating significant therapeutic efficacy.

Focused ultrasound therapy is a minimally invasive and safe new technique that can precisely target lesions while rapidly raising the temperature, making it particularly suitable for patients without surgical indications. However, the patient's ribs can limit ultrasound localization, so its clinical application is still being explored. Li et al.[91] used this method to treat 151 patients with advanced liver cancer and found that the treated patients had significantly higher levels of alpha-fetoprotein, better symptom scores, and higher 1- and 2-year survival rates compared with the control group. Nevertheless, further research on this treatment method is still needed.