Heating or freezing the tumor away: thermal ablation in lung cancer

This review examined the use of thermal ablation techniques as treatment for patients with lung cancer.

Lung cancer is one of the most commonly diagnosed type of cancer. For those diagnosed at early stages, surgical removal of the tumor is the best option for optimal survival. However, lung cancer is often not diagnosed until it is at an advanced stage, when surgery is not feasible. Roughly 20% of early-stage lung cancers are also not operable due to other health problems of the patient. Therefore, other treatment options are essential. Thermal ablation is a newer treatment that uses intense temperatures, both hot and cold, delivered directly to the cancer cells to kill them. The focus of the current review is several thermal ablation techniques such as radiofrequency ablation, microwave ablation, and cryoablation, as well as a newer technique, electrochemotherapy, and their use in lung cancer treatment.

During radiofrequency ablation an electrode delivers an electric current to the cancerous tissue, heating it to temperatures between 149 and 220 degrees Fahrenheit, thus killing the cancer cells. Clinical trials have found complete ablation (removal) of the cancerous cells in 38 to 67% of patients. A review of this technique reported 1-year survival rates of up to 85%, and 3-year survival rates of up to 46%, with local recurrence (return of the cancer) rates ranging from 3 to 38%.

Microwave ablation uses electromagnetic waves to heat the cancerous tissue, leading to cell death. Few studies have examined this technique in lung cancer. One trial noted that 25% of patients had a complete ablation of the tumor, with no incidences of local recurrence. A second analysis found 1-year survival rates of 65%, and 3-year survival rates of 45%.

Cryoablation uses extremely cold temperatures, in which the tumor cells are frozen and thawed in a repeated cycles, leading to cell death. One study showed a 99% success rate of this technique in tumors smaller than 4 centimeters. A second study found a complete response in 10% of the patients. Local recurrences were seen in 35% of patients within 21 months of treatment.

Overall, these ablation techniques have been found to be effective in patients with small, early-stage tumors not located near major blood vessels, as they can lead to tissue damage beyond the tumor. The most common negative effect associated with these treatments was pneumothorax (the accumulation of air around the lung, causing the lung to collapse), interfering with breathing. Other adverse effects included infection, cough, and fluid in the lungs.

Electrochemotherapy is a new treatment that has been tested in other types of cancer. It uses an electrical current to make cancer cells more permeable to chemotherapy (it allows chemotherapy agents to enter more easily cancer cells). This can greatly increase the effectiveness of the chemotherapy, with one study showing a 700-fold increase in the effectiveness of the agent bleomycin. Studies have shown a 78% complete response rate in melanoma patients, and a 54% complete response rate in breast cancer. However, this technique has not, as of yet, been studied in lung cancer.

This study concluded that thermal ablation techniques are useful for patients with small, early-stage tumors. Treatments such as electrochemotherapy need to be examined further as a potential therapy for advanced cases.