Studies involving the thermal (heating) mode for the treatment of pancreatic cancer have generally concentrated on radio waves. This form of “surgery” is called ablation – and of course is not surgery at all, but the destruction of tumor tissue by heating it to levels that cause cell death. Generally, the range of 120 to 140 degrees (Fahrenheit) will cause coagulation and then cell death in a matter of minutes. Temperatures above this will cause immediate tissue death.
Radio waves and microwaves can each heat tissues to these levels, but their mechanisms are quite different. Radiofrequency ablation (RFA) relies on electrical current running through the tissue in the form of a complete circuit. It works because ion rich fluid permeates the human body. And as tissue is not a perfect electrical conductor, a resistive rise in temperature occurs.
Microwave ablation is a form of dielectric heating based on an alternating electromagnetic field, and in which the tissue itself is the dielectric material. Water molecules in the tissue are forced to oscillate, with some bound molecules oscillating out of phase – causing energy to be converted to heat.
Thus microwave heating tends to occur in the space around the applicator wand, while radio frequency heating is limited to specific areas created by high electrical current. Radiofrequency ablation (RFA) has increasingly been shown to be an effective modality in the treatment of tumors in such organs as the liver, lung and kidney. But due to its reliance on tissue properties, RFA can be somewhat limiting. Microwaves are less effected by tissue properties and offer very good penetration. However, there has not been a long history with commercial or academic microwave systems, and correspondingly there have been less studies involving microwave ablation for the treatment of cancer.
So it is with great interest that we read the recent research by Carrafiello and colleagues from the Division of Interventional Radiology, Department of Radiology at the University of Insubria in Varese, Italy as published in the October issue of the Journal of Vascular and Interventional Radiology which reports on microwave ablation for pancreatic cancer.
The researchers treated ten patients who had adenocarcinoma located in the head of the pancreas with a microwave generator for ten minutes at intervals up to 12 months. The tumor response was measured, and the safety and effectiveness of the procedure was evaluated.
The authors report that the procedure was feasible in all of the patients. They indicate that there was one major complication which occurred but was resolved. That the patients quality of life tended to improve after the microwave applications, but that this tended to revert to pre-procedure levels in weeks to months after the intervention. They conclude the microwave ablation appears to be encouraging and feasible in the palliative care of pancreatic cancer.
This is an interesting study of an under-studied intervention. Microwave ablation in the treatment of pancreatic cancer deserves further inquiry.
Dale O’Brien, MD