The technology used in capacitive hyperthermia has changed very little since its invention in 1916, and its future is in question. The advent of computerized controls and motorized applicator arm has done little to change the way energy flows between electrodes, nor has it improved treatment outcomes. The replacement of wet cotton rags, for current connection, with a water bolus is probably the only real advancement forward of this aging technology. Issues like the inability to steer or shape the heating zone, the inability to increase focus or accuracy, may never be solved.
Q: What are three things Capacitive Hyperthermia and the Pop-up Toaster have in common? (answer at the bottom)
The future of hyperthermia is in Phased Array Radio Frequency. Phased Array RF is a superior heating method, according to a recent study “A comparison of the heating characteristics of capacitive and radiative superficial hyperthermia” by Kok and Crezee. The ability to focus, steer and size the heating zone, monitor and maintain zone temperature, use numerical modeling for treatment planning, is all part of this advancing technology. There is a reason that there are so few positive phase III studies using capacitive systems, the heating method is difficult to quantify. The introduction of non-invasive thermometry using MRI has created a new interest in hyperthermia. These advancements are giving researchers new tools and clinicians more resources to help cancer patients. The chances for a positive cancer outcome is simply getting better.
Capacitive Heating has several flaws.
- Fat layer power absorption.
Capacitive heating applies 10 times more power per cubic centimeter in surface fat than in tissues below the fat layer, such as tumors. This leads to significant patient discomfort and pain during treatments. The power absorbed within a 1 cm surface fat layer is equivalent the same power distributed over the next 10 cm of tissue. If you administered 200 watts of power, 100 watts would be stuck in the fat layer generating a hot spot, the remainder of the energy ( only 10 watts per cm) is spread over the next 10 cm in depth. Certainly not enough energy to heat a tumor. How many of your patients have more than 1 cm fat layer? Check out the world obesity figures.
- Field Shape.
It is very difficult to create an accurate treatment plan when you can not control field shape. Capacitive RF heating fields diverge as they penetrate in the body unless the high water content pathways are constrained by low water tissues such as bone structures of the pelvis. The only control of the shape of the heating pattern is by the placement and sizes of the electrodes used.
- No Future as an Image Guided Therapy.
Although temperature sensors are available as an option (although rarely used) on capacitive hyperthermia systems, there is no ability to respond to the distribution of heating during a treatment. The operator can change the amplitude of the RF power and the temperature of the electrode cooling bolus. This limits the possible benefit of invasive or non-invasive thermometry methods. Although one could build a system that would fit inside an MRI, the operator would only be able to turn the power up or down. There would be no ability to guide the treatment zone to the target area. It would be like driving a car that only had an accelerator, but no steering wheel.
- Is your product Hyperthermia?
In the U.S. the term "bait and switch" refers to companies that attract you with features and benefits of one product only to try to sell you an inferior product when you arrive. One manufacturer of capacitive systems does such a poor job delivering a thermal dose that they must “bait” the customer with well-known hyperthermia studies only to “switch” technologies with unproven claims that fractal frequency kills cancer cells. 30 years of hyperthermia research, 17 phase III clinical studies and hundreds of peer-reviewed clinical studies agree the active effects are due to temperature, not frequency modulation.
When presenting Pyrexar technology to a customer, you are offering a future.
Statement: Phased Array Radio Frequency systems are generally more expensive. Reason: The axiom "you get what you pay for" plays well here. You are paying for superior equipment proven by years of published data and tens of thousands of patient treatments.
Statement: Phased Array Radio Frequency systems require more training to treat patients. Reason: We wish it could be a push of a button like a chest X-ray, but effective results require proper treatment planning and simulation, similar to a Linear Accelerator, for vastly superior patient outcomes.
Statement: Phased Array Radio Frequency has a future. Reason: Continuing research and the advancement of software, a simple update can make your existing system work better and better.
- Question: If you or your loved one was diagnosed with cancer, which technology would you choose? Maybe good enough, or the proven best.
The answer to the Quiz Question: They were both invented 100 years ago, the technology has advanced little in 100 years, and Capacitive Hyperthermia technology nowhere to go.