The future is proton therapy

In this article, Professor Manfred Herbst, health director of the Proton Therapy Center, discusses the impact proton therapy is having on the treatment of cancer

Despite the progress that has been achieved using modern methods of therapy, the number of people being diagnosed with cancer in the world each year has leapt to more than 14 million, according to recently-revealed figures from the World Health Organization.

The therapy itself is painless and it gives patients a better chance of complete recovery and of returning to a higher quality of life, coupled with a stronger probability of long-term survival and getting patients back to their daily routine

The data for 2012 shows a marked rise on the 12.7 million cases recorded in 2008. In that time, the number of deaths from cancer has also increased from 7.6 million to 8.2 million.

In developed countries, cancer rates are traditionally at their highest. Approximately one in three people suffer from malignant disease, and one in five dies of it.

Radiotherapy has long been one of the most-effective and economical methods of treatment for malignant diseases with a relatively high rate of effectiveness. In developed countries, it is currently used in 50-60% of patients with malignant tumours. Of this number, a third are treated exclusively with radiotherapy and almost two thirds with radiotherapy in combination with surgery, chemotherapy, hormonal or biological targeted therapy.

Changing landscape

In more recent times, a completely new form of radiotherapy, proton therapy, has emerged. Proton therapy is based on the use of positively-charged elementary particles of hydrogen atom nuclei, namely protons that have a weight much higher than that of electrons.

Protons are accelerated in a cyclotron device to a speed equal to approximately half the speed of light. This also determines their energy, which reaches up to 230 mega-electron volts (MeV) and enables them to damage tumours up to a depth of approximately 30cm. The protons are then targeted with a strong magnetic field into a very narrow beam - a pencil beam - and transferred with a high degree of accuracy via a 3D image to the malignant tumour. The energy from them is released during deceleration in the tumour tissue with subsequent ionisation and damage of the DNA of the affected cell. If the damage is sufficient, the cell stops dividing and growing or dies immediately.

Scoping the benefits

During conventional radiation, the beam of photons transfers the greatest dose of radiation to the front of the tumour. Afterwards, the radiation penetrates the tumour and the tumour itself is irradiated with less energy than the tissue before the tumour. The healthy tissues behind the tumour are also irradiated and the radiation gets out of the body on the opposite side of the entrance with up to 40% of its primary energy. In contrast, proton therapy uses accelerated particles and the primary energy level which has a high energy level can be sleeved and accurately targeted to the tumour. The greatest part of the proton beam’s energy is transferred solely to the tumour, where it has maximum destructive effect. The beam is totally targeted to the tumour and protects healthy tissue behind the tumour from any damage.

Since current proton therapy technology enables irradiation with a proton beam from whatever necessary angle and the irradiation may be well modulated, it is possible to protect vital organs near the tumour completely without any damage.

Since current proton therapy technology enables irradiation with a proton beam from whatever necessary angle and the irradiation may be well modulated, it is possible to protect vital organs near the tumour completely without any damage

Taken together, these features also mean that proton beams are well suited to being used for the treatment of malignant tumours where therapeutic possibilities are restricted and conventional radiotherapy is associated with a high risk of adverse effects. This is particularly the case with childhood tumours, eye tumours and those in some areas of the brain.

The qualities of the proton therapy approach also mean that it has only minimal or no side effects. The therapy itself is painless and it gives patients a better chance of complete recovery and of returning to a higher quality of life, coupled with a stronger probability of long-term survival and getting patients back to their daily routine.

It is also worth highlighting that contrary to popular belief, proton therapy is, in practical terms, often cheaper than conventional radiotherapy. The actual cost is typically slightly more than traditional radiotherapy, but with proton therapy there is nearly no need for additional ad hoc treatment of collateral damage including the long-term side effects of treatment. This saves costs.

The latest innovative pencil beam scanning, one of the most-precise tools available to oncologists in the fight against cancer today, is now taking proton therapy to a new level. The approach makes it possible to deliver an even more precise dose of proton therapy to further minimise exposure of healthy tissue to radiation and allow radiation oncologists to better treat more complex tumours. Very few facilities are currently using this approach. At the Prague Proton Therapy Center, we were the third to employ it for our daily routine.

Looking ahead

For decades in oncology, practitioners have been striving to maximise the effectiveness of treatment while maintaining quality of life, ie minimising the side effects of cancer treatment.

Traditional radiotherapy has gone a long way towards achieving this objective, but today the focus is on delivering the highest dose of radiation possible to tumour areas while protecting nearby healthy tissues. Proton therapy fully complies with this objective and is today making a significant contribution to tackling many different types of cancers successfully, with new indications and higher cure rates, enhancing the quality of life of patients and improving survival rates.