New Cancer Treatments Made More Powerful with Fewer Side Effects

Scientists are having initial success in new combined therapies to deliver cancer treatments that target only the tumor without damaging normal tissue.

One new therapy uses nanoparticles, such as carbon nanotubes (CNTs), for drug delivery. Another new therapy that has been used is nonthermal irreversible electroporation (N-TIRE). The principle behind this therapy has been known since 1898 as a method to treat bacteria-infested water, but it is now being used in the treatment of cancer. N-TIRE is the application of electrical fields to a targeted tissue area with the purpose of permanently opening pores in the membranes of a cell, causing cell death. The destruction of the cells in this instance is not due to thermal injury--significant since it allows the elimination of tumor cells while respecting normal tissue.

Dr. Rafael Davalos, a bioengineer at Virginia Polytechnic Institute and State University (Virginia Tech; Blacksburg, USA) and coinventor of N-TIRE, is doing a study combining N-TIRE and CNTs. He is using N-TIRE to treat the tumor and CNTs to target selectively cancer cells inside a tumor and cancer cells that have already moved throughout the body. "The procedure is essentially done with two minimally invasive electrodes placed into the targeted region," Dr. Davalos said, "delivering approximately 80 pulses to the site in about one minute. The pulses are high voltage, but low energy, so no significant heating occurs as a result of the procedure."

Lack of heat is important for structures such as nerves and major blood vessels, according to Dr. Davalos, as this preserves the tissues and allows treatment of previously inoperable tumors. Although the procedure has submillimeter resolution, he adds, the injected nanoparticles improve targeting even further.

Typically, most studies report minimal side effects in the treatment with N-TIRE, but there are some apprehension about therapies with CNTs, since researchers have seen some effects such as excessive inflammatory response and formation of free radicals in some trials. "N-TIRE can be safely used right now," Dr. Davalos said. "However, if we combine N-TIRE with another therapy, we need to be careful with the choice of nanoparticle to ensure no toxicity to the body."

N-TIRE was utilized for the first time in humans in 2008 for prostate cancer treatment, with promising results. New trials are being conducted for lung, kidney, hepatic, and other cancers. Carbon nanotubes, hypothetically, are very promising as a cancer therapy, but more research needs to be done to address toxicity. "The combined therapy of CNTs plus N-TIRE can be used to treat any type of cancer including brain, prostate, kidney, liver, and pancreatic, but is limited in that it is a focal technique," Dr. Davalos added. "In other words, only one 2 cm to 3 cm site can be treated at a given time. One of the objectives of the research is to increase the zone that can be treated using a single procedure."

Similar to any focal treatment, this combinatorial therapy will typically be used in conjunction with a traditional treatment, until its efficiency can be broadly demonstrated. "This technique would most likely be used in conjunction with other therapies that are the standard of care," Dr. Davolos said. "However, it can be used independently, and also can be used as a salvage therapy when other techniques are no longer effective."

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Virginia Polytechnic Institute and State University