Treating brain tumours

A CHEMICAL agent long used by physicians to get detailed pictures of cancer tumours may also have therapeutic value for a class of deadly brain tumours, according to a new study.

The study, published in the Cancer Research, demonstrates that gadolinium compounds, contrasting agents used in Magnetic Resonance Imaging (MRI) to illuminate tumours, can be absorbed by cancer cells where, in combination with thermal neutron treatment, they can destroy the DNA that cancer cells depend on to live and reproduce.

"It's like a small atomic bomb," says Gelsomina De Stasio, a University of Wisconsin-Madison professor of physics and the lead author of the study. "There is going to be a very strong and very destructive reaction where the gadolinium is situated" when it is exposed to low-energy neutrons while sparing nearby healthy tissue that does not contain gadolinium.

Gadolinium has been used for more than 15 years in MRI as a contrast agent to light up the tumour cells. But it has long been assumed to have no therapeutic value because it was thought that it could not be absorbed by cancer cells. The new study shows, however, that gadolinium is indeed absorbed by cancer cells where it migrates to the nucleus and can be triggered by thermal neutron radiation to destroy the cancer cell DNA.

The results of the study, conducted at UW-Madison's Synchrotron Radiation Centre, suggest that new gadolinium-compound therapies could be developed to treat glioblastoma, a brain cancer that kills an estimated 12,000 people every year in the U.S. alone. "It's a very nasty tumor and usually kills patients within six months of diagnosis," De Stasio says.

In the past, similar therapies employing boron compounds have been attempted, and are used widely in places such as Japan. But gadolinium compounds seem to be much more specific for tumor cells and, once absorbed into the cell nucleus, provide a much bigger target for the neutrons that provoke the DNA-destroying reaction.

The study was conducted in cultured tumour cells. Therapies involving gadolinium compound isotopes have not yet been tried in humans, but studies of how well the compounds are absorbed by tumor cells in patients are now underway. If successful, the new studies could lead to a non-invasive and non-toxic treatment for glioblastoma patients.

Gadolinium compounds used in Magnetic Resonance Imaging (MRI) to illuminate tumours, can be absorbed by cancer cells which, in combination with thermal neutron treatment, can destroy the DNA that cancer cells depend on to live and reproduce.

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