Malignant gliomas (glioblastoma, GBM) are difficult to treat. Our current methods of treatment – surgery, radiotherapy and chemotherapy – all help but are ultimately not curative. New treatments are desperately needed.
In recent years, a new form of treatment has been developed which may have a role in the future – Tumour Treating Fields (TTFields). TTFields are low intensity, intermediate frequency electric fields that slow cell division therefore inhibit tumour growth. This treatment was developed after it was shown that cancer cells in culture (i.e. in the laboratory) were stopped from dividing and then were killed by these electric currents. Animal models were then used to show a positive effect and the technology was then first used in patients with cancer less than 10 years ago.
TTFields started to be used for brain cancer a short time after that. Now, 2 large international, multicentre trials have been published examining the effect of TTFields. The first trial examined whether there was a benefit in patients with recurrent or progressive GBM (EF-11 trial, Stupp et al., Eur J Cancer 2012). This group of patients have a notoriously difficult problem and very few options are available. TTFields do not seem to provide significant benefits in this group.
The EF-14 trial was an international randomized study for patients with newly diagnosed GBM (glioblastoma) comparing the outcomes of patients treated with standard post-radiotherapy chemotherapy to those who also had TTFields (Stupp et al., JAMA, 2015). There did appear to be some benefit – TTFields did appear to slow the tumour in some patients. Recurrence was delayed, and on average, overall survival was a little better (19.6 months vs 16.6 months). There are also valid criticisms to the design of this trial and it could be that other factors – rather than the TTFields themselves – were at play.
But even if TTFields were having some positive effect, they are not a magic cure. In the EF-14 trial, at 18 months after treatment, the tumour had recurred in about 80% of patients whether they had TTFields or not. Whilst overall survival was better at 2 years for the TTFields group, that benefit soon evaporated, and the survival rate did not seem to be any different by about 3 years. About 20% of all patients were still alive at 4 years – there was no benefit from TTFields by this point.
There is still a lot to learn about the possible role of TTFields and many trials are ongoing. I am not convinced that this form of treatment will play a major role in the future however.
Prof David Walker is a neurosurgeon and spinal surgeon at BrizBrain & Spine. He has a special clinical interest in brain tumours and is actively involved in conducting research to help find a cure for this disease. Prof Walker is also the Managing Director of the Newro Foundation, a research organisation that conducts research into brain and spine conditions.