Chemotherapy can help in the fight against certain forms of brain cancer, although the treatment is far from ideal and improving brain cancer survival rates is notoriously difficult.
Brain tumors are particularly difficult to treat and oncologists’ attempts to improve brain cancer survival rates have largely failed. Around 15 years ago, a new chemotherapy drug called temozolomide was introduced, although relatively little progress has been made since then.
However, on Friday last week, the results of a large-scale clinical trial of the use of Novocure’s Optune tumor-treating fields (TTF) were announced and the results are extremely promising. The new treatment could signal one of the most important advances in the treatment of brain tumors since the introduction of temozolomide, and most importantly for patients, Novocure’s treatment does not cause the collateral damage associated with chemotherapy drugs.
Novocure conducted the trial on 695 glioblastoma patients. After two years, 43% of patients had survived compared to 30% of patients who had not had the treatment. After four years, survival rates dropped to 10% for patients who did not use the system, while Optune patients’ survival rate was 17%. As Doyle puts it, “To patients, that’s a big difference.”
The Optune system uses low-intensity AC electric fields to prevent cancer cells from dividing and spreading. Molecules inside cells are polarized and are therefore affected by electric fields. By applying electric fields to the brain, the process of mitosis is disrupted.
When cancer cells divide and form an hourglass-shape, the TTF fields are concentrated at the pinch point. The electric fields pull molecules inside the cell into the wrong position, or as Novocure’s executive chairman explained, “all hell breaks loose in the cells.” Dividing is prevented and many of the cancerous cells go into a “state of programmed cell death.”
However, cancer cells are not the only cells in the body to undergo mitosis, so if the process is disrupted, why does this not happen in all cells. The trick is to very carefully target glioblastoma cells by using a very precise frequency for the electric field, which in the Optune system is 200 kHz.
Doyle’s says that the membranes of cells act in a similar way to a capacitor. In order for the electric field to pass through the cells, the frequency must be correct. Cellular membranes have specific filtering properties. At 200 kHz, the electric fields pass through the glioblastoma cells but not through normal brain cells or neurons, thereby targeting the cancerous cells without causing any collateral damage. Although Doyle does point out that the process is helped by the fact that there is little cell division in the brain.
However, that said, it may still be possible to treat other cancers, provided that the Optune system can be shown to allow the same level of precise targeting.
The system is not without its drawbacks. The cancer patient must have the electrodes strapped to their heads for around 18 hours a day and the system is not light. The first-generation device weighed about 6 lbs. (3kg), although a new model has just been released that is 2.7 lbs. (1.2kg) and can be carried in a shoulder bag. The device must be charged every few hours or a replacement battery pack connected.
It has been difficult to gain approval to use the new treatment method on brain cancer patients. The treatment method was approved in the United States in 2011, but only for patients with recurrent glioblastoma who had no other options. It took a further four years for the treatment to be authorized for patients who had just been diagnosed with glioblastoma. Even though the treatment appears to be effective, oncologists have been slow to start recommending the system. However, the results of the trial may now change that.
Image Source: Novocure