Adelaide’s historic link to X-ray discovery comes full circle

Tumours can be precisely targeted with proton beam therapy without damaging the surrounding tissue. Credit: HZDR / AIFilm HEALTH
Tumours can be precisely targeted with proton beam therapy without damaging the surrounding tissue. Credit: HZDR / AIFilm

In 2021, the first proton therapy unit in the southern hemisphere will open in Adelaide. The treatment will revolutionise cancer therapy in Australia, says UniSA Professor of Medical Radiation, Eva Bezak.

Professor Eva Bezak talks about the impact proton therapy will have for cancer patients when it opens in 2021.

In November 2018, a US court awarded more than $25 million to the family of a brain cancer patient who died after being denied proton beam therapy (PBT) by her health insurer, despite its recommendation by her doctors.

The reason given by the insurer for refusing to fund the treatment was that it was “experimental”. A jury found otherwise, endorsing PBT as effective and medically necessary in this instance.

The court finding and the growing acceptance of PBT for cancers with limited treatment options hopefully means that Orrana Cunningham’s death was not in vain.

Certainly, in the US and UK, demand for the treatment – particularly for paediatric cancer patients – is increasing, with 27 proton therapy centres now operating in the United States and two in the United Kingdom.

Australia is yet to enter the PBT field, but this will change in 2021 when the first proton therapy unit in the southern hemisphere opens in Adelaide.

UniSA Professor of Medical Radiation, Eva Bezak, says the Australian Bragg Centre for Proton Therapy will consolidate Adelaide’s position as the leading biomedical science cluster south of the equator.

The unit is expected to throw a lifeline to about 500 cancer patients in Australia whose treatment options are limited on home soil.

“Proton therapy is especially appropriate for eye or brain tumours and a far more preferable option for children with cancer,” she says.

Proton beam therapy spares healthy tissues

Proton beam therapyProton beam therapy

Unlike conventional x-ray (photon) therapy, proton beam therapy directly targets tumours and cancer cells, delivering optimal radiation doses to the tumour while limiting the effects on the surrounding healthy tissues.

“Protons are designed to deposit radiation at the actual site of the cancerous tissue, sparing both the healthy tissues at the shallower depth and those surrounding the tumour.

“X-ray therapy, on the other hand, while cheap and effective in killing the cancer cells, exposes larger volumes of healthy tissues to radiation.”

While both are forms of radiotherapy, photon (x-ray) beams interact differently with matter and human living cells, depositing most of the radiation at a shallow depth and gradually losing energy until they reach the targeted site. As they leave the patient’s body, they continue to emit radiation, harming healthy tissue.

Protons are charged particles which enter the body very fast and deposit only a small dose along the way, gradually increasing with greater depth and lower speed, rising to a peak when the proton stops.

This is known as the Bragg peak – named after Sir William Henry Bragg, who discovered it in 1903 while working in Adelaide.

This historic link – with Bragg founding a new branch of science in the very city in which proton therapy will make its national debut – is significant, Prof Bezak says.

The Australian Bragg Centre for Proton Therapy will be housed on North Terrace in a new site earmarked for development next to the SAHMRI building.

“The PBT will change the way we deliver cancer treatment to children especially. The treatment is less invasive, it reduces overall toxicity, there will be reduced chance of patients getting second cancers with proton therapy and fewer side effects than with conventional radiation treatment.

“Children’s cells are more vulnerable to radiation damage than adults and proton beam therapy is less likely to lead to growth reduction, cognitive impairments and other complications later in life.”

Apart from paediatric cancers, proton therapy is also the preferred treatment option for cancers located close to the eye, brain stem, or spinal cord and others where conventional radiotherapy is riskier, Prof Bezak says.

Prof Bezak has recently co-authored a paper reviewing current global proton therapy outcomes for paediatric cancers of the central nervous system. The paper is published in Cancer Treatment Reviews.

Australian cancer statistics for some of the cancers proton beam therapy can treat

Australia has approximately 750 children diagnosed with cancer each year – the majority aged 0-4 years. According to the Cancer Council, about 100 children die from cancer each year in Australia. Leukaemia is the most common paediatric cancer, followed by brain tumours and lymphomas.

Brain cancer accounts for around 1500 deaths each year in Australia. Survival rates are low – around 22 per cent do not live beyond five years of diagnosis.

Eye cancer is rare in Australia, affecting less than 1000 people each year, and usually caused by melanoma.