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September 15, 2003

Radiofrequency Ablation: A Minimally Invasive Treatment that is Effective for Both Large and Small Tumors
Jason R. Williams, MD

Radiofrequency (RF) ablation is a minimally invasive procedure that can be used to treat tumors in the lung, liver, kidneys, adrenals and bones. The procedure involves placing a special needle into a tumor using image guidance (usually CT). RF energy is sent through the needle which results in the generation of heat. It is the heat from RF energy that results in the destruction of the tumor.

RF ablation is usually considered for tumors that are less than 4 cm in size. However, we have been having success with ablation of large tumors (up to 16 cm). This is significantly larger than what was previously considered an appropriate size of tumor to treat. We have found that ablation of tumors ranging from 5-16 cm can be successfully performed.

Previously it was felt that ablation of large tumors might leave too much residual live tumor behind. This is due to the fact that multiple needle repositioning is required to achieve the necessary overlapping that is required to treat a larger tumor. This overlapping can result in missed areas of tumor. However, new techniques can help achieve a more complete ablation. This new technique involves mapping of the tumors with a PET/CT. A PET/CT scan can demonstrate the precise location of active tumors. A PET/CT is different from a PET or a CT scan. Images from PET and CT are obtained at the same time by a combined PET/CT scanner. This allows for accurate overlapping of the PET and CT data. This results in an image which gives the anatomic detail of a CT scan with the metabolic activity which indicates tumor viability. This can help determine the difference between treated and untreated tumor.

The ablation of a large tumor can be beneficial for several reasons. Large tumors typically do not respond well to chemotherapy and radiation. Chemotherapy may not be effective for the central part of some larger tumors. This same problem can also be seen with radiation. There are several factors involved in making the central portion of the tumor more resistant to chemotherapy and radiation. The central part of the tumor tends to have a reduced blood flow, as compared to the outer portion of the tumor. This results in continued starvation of the tumor for oxygen. The tumor cells respond by several survival mechanisms. The tumor releases substances to increase blood vessel growth (angiogenesis). They are more likely to spread (metastasize) to areas with improved oxygenation. These factors result in the tumor becoming more aggressive.

RF ablation is a minimally invasive procedure that is effective in destroying most or all of a tumor. This can significantly improve the patient's response to other therapies. The tumor can be targeted more effectively using PET/CT mapping. Radiofrequency ablation has achieved success in the treatment of tumors up to 16 cm in size. The treatment of large tumors has the potential to reduce its aggressiveness. This could greatly alter the patient's prognosis in a positive manner.

Jason R. Williams, M.D. American Institute for Cancer Ablation Gulf Shores, Alabama

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