Tumor Treating Fields (TTFields)

The system consists of a small battery-powered field generator, a set of connecting cables and adhesive arrays holding ceramic discs that are applied to the skin over the region to be treated. It delivers alternating electric fields of low intensity at frequencies in the hundreds of kilohertz, chosen for the cell type being targeted. These fields are not felt as an electric current; the sensation is a mild warmth under the patches. Because the effect is produced by the field itself rather than by a substance carried in the blood, the treatment acts only where the arrays are placed and does not circulate through the body. The device records how many hours a day it is worn, and this figure is reviewed at every clinic visit because the benefit is closely related to it.

Dividing cells rely on a structure called the mitotic spindle, built from microtubule proteins that carry a strong electrical polarity. Alternating fields at the right frequency exert forces on these polar molecules, interfering with the assembly of the spindle and with the constriction that separates the two daughter cells at the end of division. Cells caught in this state either fail to divide, divide abnormally or undergo programmed cell death. Cells that are not dividing are largely unaffected, which is why healthy tissue in the treated region tolerates the fields. The arrays are positioned according to a plan generated by software that maps the field through a model of the individual patient's head or body built from their own magnetic resonance images, so that the strongest field falls across the tumour. The arrays are changed every few days and the position is adjusted as the imaging changes.

The best-established use is newly diagnosed glioblastoma, where the device is started after surgery and radiotherapy and worn alongside maintenance chemotherapy, and it is also used for recurrent glioblastoma. It has been studied and applied in selected other solid tumours, including certain lung and pleural cancers, where a field can be applied across the affected region. It helps patients who want an additional line of treatment that does not add systemic toxicity, and it is particularly suited to those who are otherwise well enough to continue ordinary activity while wearing the device. It is not appropriate for people with an implanted electronic device in the treated region, with a skull defect that alters the field, or who cannot manage the practical demands of daily wear. A neuro-oncology or oncology team decides suitability and supervises the treatment.

The main appeal is that it adds anti-tumour effect without adding the side effects of another drug: there is no nausea, no hair loss from the treatment itself, no suppression of blood counts and no radiation dose. Life continues at home, at work and while travelling, with the device carried in a shoulder bag and charged overnight on mains power. The practical demands are real. For head treatment the scalp must be kept shaved so the arrays adhere, the arrays are replaced every few days, usually with help from a family member or nurse, and the target of around 18 hours a day requires planning. Skin under the patches can become red, itchy or sore, and this is managed by rotating the array position slightly, using prescribed creams and keeping the scalp clean. Clinical trials in glioblastoma reported improved progression-free and overall survival when the device was added to standard chemotherapy, with the benefit greatest in those who wore it for the highest number of hours a day. Response is assessed with routine imaging in the usual way.