Physican Information: Tumor Ablative Therapies Explained

September 9, 2006

At its most basic, tumor ablation is a method of destroying a tumor without major surgery. A needle electrode guided to and inserted inside the tumor produces either extreme heat or extreme cold, which destroys the tumor from the inside out. The treatment is focused on a very small area, so only the tumor and a safety margin of surrounding tissue are destroyed. The majority of healthy tissue in the organ is unharmed.

Types of Tumor Ablation
The most common method of destroying a tumor with heat is radiofrequency ablation (RFA). With this method, the needle electrode inserted into the tumor produces radio waves. These radio waves agitate the molecules in the tissue around the needle electrode tip; that friction heats the tissue to at least 50 degrees C, which kills the tumor.

Laser ablation is similar to radiofrequency ablation, but instead of a needle electrode, a fiber-optic cable is guided into the tumor. The cable is used to fire a laser into the tumor. This method has proven to be less effective than RFA.

Other methods of destroying a tumor with heat are microwave ablation and high-intensity focused ultrasound. Microwave ablation uses the different water content in tumor cells versus healthy cells to target a microwave only to cancerous cells. It is showing great promise and is preferred by some investigators; it is, however, a newer technology and is available at only about a dozen research sites in the U.S. High-intensity focused ultrasound uses tightly focused ultrasound beams to heat and destroy the tumor. Both these methods are less tested than RFA.

Cryotherapy involves the use of a needle electrode inserted into the tumor to freeze the tissue to below –20 degrees C. This forms an ice ball around the tumor, which, like heat, kills the tissue.

RFA is the most commonly used method of destroying tumors and has shown the most success.

Patient Profile
Tumor ablation techniques can be safely used for patients who are not surgical candidates, such as those who have already undergone major surgery, or those who have suppressed immune systems or an increased risk of bleeding. Because the method destroys only the diseased tissue plus a margin of safety around the tumor, it is much more forgiving than surgery or systemic treatments such as radiation or chemotherapy.

Location of Tumors
RFA has been most often studied in relation to liver tumors. It is also used to treat tumors in the kidney, breast, bone, lung, lymph nodes, nerve ganglia, and soft tissue.

RFA and other heat-ablative methods may not be ideal in some cases, because the heat can damage nearby nerves or cause thermal stricture. In such locations, including the prostate or certain areas of the kidney, cryoablation can be used as a substitute.

Tumor ablation methods are not recommended for treatment of tumors of the colon, stomach, or other hollow organs.

Size of Tumors
RFA and other tumor ablation methods are most successful at eliminating tumors that are between 0.5 and 3 centimeters in size. The technique can also be used to de-bulk larger tumors, making them more susceptible to other treatments, such as chemotherapy and radiation therapy. In addition, RFA and other ablative methods can be used to reduce the size of tumors that threaten to grow too large and preclude the possibility of transplant.

Number of Tumors
Tumor ablation has been most successful in treating three or fewer tumors per organ. The procedure can be used to treat more tumors in a site, but survivability rates are lower.

Pain Management
Tumor ablation can be used to reduce or eliminate painful bone tumors that cannot be treated with other methods. It can also shrink large tumors that may be encroaching on nerves or otherwise causing pain.

In addition, RFA and other ablative therapies can help improve the quality of life for patients with cancer that cannot be treated. The techniques can be used to shrink or destroy painful soft-tissue tumors that are causing pain, even if the patient does not have a high chance of survival.