Researchers have shown that electrical stimulation to the skull can starve brain cancers of vital nutrient-rich blood, opening the door to “brain zapping” as a new treatment for the often-fatal tumours.
Transcranial direct current stimulation (tDCS) applies a low intensity electrical current to the brain via electrodes on the scalp and is being investigated for a range of disorders including depression, speech loss after stroke, and the cognitive decline of Alzheimer’s disease.
It has not, however, been used for brain tumours.
A team from Harvard Medical School, US, and Italy’s University of Siena enrolled eight patients for the recent study. Six had glioblastomas – tumours that grow from the brain tissue itself – and two had metastatic cancers that had spread from the lung.
Even with the gold standard treatments of surgery, chemotherapy and radiotherapy, the outlook is grim for both types of cancer. Median survival is around 12 months.
The researchers, led by Harvard’s Emiliano Santarnecchi, used brain scans to map the tumour and guide placement of scalp electrodes with the aim of maximising current to the cancer and minimising effects on the surrounding brain.
Each patient then had 20 minutes of tDCS while in a functional MRI scanner, which can monitor blood flow in the brain.
For such a brief intervention, the results were dramatic.
Blood flow to the tumour reduced by an average 36%, ranging from 26% in the patients with glioblastoma to 45% for the patients with metastases. Apart from some reported tingling when the stimulation began, which is common in tDCS, there were no reported adverse effects.
Aggressive cancers grow rapidly and depend on nutrients from a liberal blood supply, hence the use of tumour perfusion as an index of just how nasty they are.
It’s also the rationale for treatments called “embolisation” that work by blocking blood flow to tumours, typically liver cancers. tDCS might work in a related way for brain cancers, write Santarnecchi and colleagues.
“Occlusion and vasoconstriction of the vessels in proximity to the electrodes have been considered the principal effects of electrotherapy, caused by electrolysis,” they write.
Indeed, they add, all that blood coursing through tumours makes them uniquely susceptible to tDCS, because it renders them better conductors of current than adjacent, less well perfused parts of the brain.
It’s worth noting this was a proof-of-concept study and, at least in part due to small patient numbers, did not measure tDCS effects on patients’ outcomes. The authors report that only two patients were still alive at time of writing. The other six died on average 10 months after their initial MRI diagnosis.
Nonetheless, the researchers say they will push ahead with further studies to assess the effect of repeat tDCS sessions, whether it works better combined with chemotherapy and radiotherapy, and if it has effects on other types of tumours.
“Results potentially open the door to non-invasive therapeutic interventions in brain tumours based on stand-alone transcranial electrical stimulation or its combination with other available therapies,” they conclude.
The study’s findings are reported in the journal Science Advances.
Paul Biegler is a philosopher, physician and Adjunct Research Fellow in Bioethics at Monash University. He received the 2012 Australasian Association of Philosophy Media Prize and his book The Ethical Treatment of Depression (MIT Press 2011) won the Australian Museum Eureka Prize for Research in Ethics.
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