PORTLAND, Ore. Curing cancer is usually the domain of medical doctors, but now biomedical engineers at Virginia Tech and the University of California at Berkeley have invented a promising electronic therapy. Using short electrical pulses that target only cancer cells, together with real-time monitoring via electrical impedance tomography, the procedure has already been shown to cure cancer in lab rats. Currently the group is treating mice, and human trials are slated for 2008.
"We have invented a new, inexpensive, minimally invasive surgical technique that makes use of irreversible electroporation, essentially killing cancer cells with short electrical pulses, while leaving neighboring healthy cells unharmed," said bioengineering professor Rafael Davalos of Virginia Tech's School of Biomedical Engineering and Science. "We are also using electrical impedance tomography to monitor progress and make sure all the cancer cells get treated."
Work has progressed from cell cultures to rats to mice, with human trials on prostate cancer slated for next year. If human trials for prostate cancer are successful, then curing other types of cancer will be tried in humans.
Since the mid-1960s engineers have been using electroporation to take electronic control of the pores in a living cell's outer membrane. For instance, genetic engineers routinely use electroporation to load DNA sequences into cells. By using 2,500-V electrical pulses that are 100-microseconds long, pores can be opened in any cell membrane, allowing liquids to flow in and out. Other cancer researchers use electroporation to temporarily make tumor cells more permeable to cancer-killing drugs than the surrounding healthy tissue, but Davalos and UC-Berkeley collaborator Boris Rubinsky use extended sessions with the electrical pulses to essentially electrocute the cancer cells, permanently opening pores that kill the cell as its contents drain out.
"We use needle electrodes to surround the cancerous area, then we use external electrodes to monitor our progress with electrical impedance tomography, because when the pores stick open on a cell, it lowers the bulk resistance of that tissue, which we can image with sub-millimeter cell-scale resolution," said Davalos.
By treating an area while watching their progress using electrical impedance tomography, then moving the needles and repeating as necessary, the engineers have been able to treat different types of cancerous tissue in laboratory animals. The treatment takes about one minute per affected area.
"With our treatment the pulses are so short that the cells don't heat up," said Davalos.
Likewise, cryoablation freezes cancer cells, instead of heating them. Unfortunately, killing the cancer cells with cold sometimes damages nearby healthy cells, just as heat can.
"Our procedure doesn't affect neighboring cells," said Davalos. "Our treatment is also tissue independentall cells just behave in this way. All we have to be able to do is get the needles to the targeted area, and in just one treatment you are rid of the cancer."
A key problem with all cancer treatments, according to the researchers, is that oncologists cannot tell if the cancer cells are dead until a week or more after the treatment. Consequently, if oncologists are not aggressive enough during the treatment, they can miss some cancer cells. Conversely, if they are too aggressive, the treatment can damage surrounding healthy tissue and blood vessels. Using irreversible electroporation, success can be monitored in real-time with electrical impedance tomography, leading the researchers to claim their technique is more effective because it can be more accurately applied.
"With other procedures, you don't get immediate feedback on whether the area has had enough treatment yet. With ours, you can see how successful the treatment is as you go along," said Davalos.