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Laser treatment opens temporary window in blood-brain barrier

BMJ 2016; 352 doi: https://doi.org/10.1136/bmj.i1154 (Published 25 February 2016) Cite this as: BMJ 2016;352:i1154
  1. Jacqui Wise
  1. London

A laser system used to kill brain tumours also temporarily disrupts the blood-brain barrier, allowing chemotherapy drugs to pass into the brain for up to six weeks, finds a study published in PLoS One.1 The discovery may give doctors a window of opportunity to use drugs against glioblastoma that are normally ineffective, the researchers said.

Glioblastoma is the most common and lethal malignant brain tumour in adults. There is no effective long term treatment, and patients usually live for only 12-15 months after diagnosis. Up to 90% of recurrent tumours develop within a 2-3 cm margin of the primary site and are thought to arise from microscopic glioma cells that infiltrate the area surrounding the original tumour. The poor penetration of cytotoxic drugs into the central nervous system because of the blood-brain barrier is a major limiting factor in the treatment of brain tumours.

In the pilot trial 14 patients with a brain tumour underwent laser ablation, guided by magnetic resonance imaging, to kill the tumour. At the same time the patients were treated with doxorubicin, a chemotherapy drug that is normally blocked by the blood-brain barrier.

The researchers used an advanced imaging method to analyse the leakiness of the blood-brain barrier after laser ablation. They found that in all the patients the barrier was disrupted for between four and six weeks after use of the technique.

Preliminary data indicated that there could be a survival benefit to giving chemotherapy in the four to six weeks when the blood-brain barrier was diminished, the researchers said. But whether this was long enough to be therapeutically meaningful would need to be determined prospectively in future studies. The trial is part of a larger ongoing trial involving 40 patients whose results are expected within a year.

David Tran, a study author and chief of neuro-oncology at the University of Florida, said that the findings showed for the first time that the blood-brain barrier could be temporarily disrupted at tumour sites. “This gives us a very significant window of time to give chemotherapy,” Tran said. “We will be able to test a lot of drugs for effectiveness.”

Tran added that opening the blood-brain barrier also raised the possibility that immunological techniques could be used more effectively against brain tumours. With the blood-brain barrier disrupted, the tumour could be recognised more readily by the immune system and immune cells could get better access to the tumour.

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