Glioblastoma is the most common type of brain tumor affecting 0.002-0.003% of general population.
the astrocytes (neuron-supporting glial cells) turn into cancerous
cells, start to divide frequently and gradually form a large mass
pressing against the brain.
Glioblastoma is a challenging disease to treat as dosages of radiotherapy and chemotherapy are limited by their toxicity to the brain tissue.
The use of alternating electrical
fields is a novel approach that aims to suppress the division (mitosis)
of malignant cells while sparing non-dividing neuronal cells in their
An Israeli-based company NovoCure Ltd. developed a stimulation device, Novo-TTF, which delivers alternating electric fields through insulated electrodes attached on the scalp surface.
The scientific foundation of this approach comes from the study by the Technion scientists showing that alternating electrical
fields can stop the cells from dividing and can even destroy them, if
the cells are oriented roughly along the field direction. Importantly,
the dividing cells inside the blood vessels appear to be unaffected.
key concern for the therapeutic use of alternating electric fields relates to their effects on neurons. At low frequencies, under 1 kHz, alternating electric fields stimulate neurons. As the frequency of the electric field
increases above 1 kHz, the field can better penetrate through the
cellular membrane, and its effect on neuronal excitability is
diminished. At even higher frequencies, above 100 MHz, the brain exposure becomes localized and significant local heating can occur.
Faced with these possible side-effects of low and high frequencies, the scientists decided to stick with intermediate frequencies of 100–200 kHz.
The electric fields
at these frequencies might be relatively safe as long as their
intensity is kept below the threshold for inducing the pore formation in
the cellular membrane, through a phenomenon called electroporation.
recently completed phase III trial of the Novo-TTF device alleviates
some of these concerns by showing no change in incidences of headaches
or seizures in patients. The device is likely to be approved for use in
the US within the next three months.