Carbon nanotubes - hollow cylinders of pure carbon - release heat when exposed to a radiofrequency (RF) field. If the nanotubes are localized within tumours, this thermal effect will destroy the cancer cells. Without such a target, the radio waves pass harmlessly through the body.

In preclinical experiments, the researchers injected a solution of single-walled carbon nanotubes directly into liver tumours in four rabbits. The rabbits were then exposed to a 13.56 MHz RF field for two minutes, resulting in complete destruction of their tumours. No side effects were noted, although some healthy liver tissue within 2-5 mm of the tumours sustained heat damage due to nanotube leakage. Control tumours, which were treated only by RF exposure or only by nanotube injection, were unaffected.

"These are promising, even exciting, preclinical results in this liver-cancer model," said Steven Curley, professor in M D Anderson's department of surgical oncology. "Our next step is to look at ways to more precisely target the nanotubes so they attach to, and are taken up by, cancer cells while avoiding normal tissue."

Research is now underway to bind the nanotubes to antibodies, peptides or other agents that target molecules expressed on cancer cells, which would allow sole targeting of the nanotubes to the tumour cells. As RF fields penetrate deep into tissue, once this targeting is achieved, it will be possible to heat up nanotubes anywhere within the body. Curley estimates that a clinical trial is at least three to four years away.

The researchers presented their results in Cancer.