What is cancer radiotherapy, and why do we need proton beam therapy?

May 10, 2017 by Paul Keall, The Conversation
Radiotherapy treats cancer by directing beams of high energy x-rays at the tumour. Credit: shutterstock.com

In last night's federal budget, the government dedicated up to A$68 million to help set up Australia's first proton beam therapy facility in South Australia. The government says this will help Australian researchers develop the next generation of cancer treatments, including for complex children's cancers.

Proton beam therapy is radiation therapy that uses heavier particles (protons) instead of the X-rays used in conventional radiotherapy. These particles can more accurately target tumours closer to vital organs, which can be especially beneficial to patients suffering from brain cancer and children whose organs are still developing and are more vulnerable to damage.

So, the facility will also be an alternative to conventional radiotherapy for treating certain cancer. But what is traditional radiotherapy, and how will access to improve how we manage cancer?

What is radiotherapy?

Radiotherapy, together with surgery, chemotherapy and palliative care, are the cornerstones of cancer . Radiotherapy is recommended for half of cancer patients.

It is mostly used when the cancer is localised to one or more areas. Depending on the cancer site and stage, radiotherapy can be used alone or in combination with surgery and chemotherapy. It can be used before or after other treatments to make them more effective by, for example, shrinking the before chemotherapy or treating cancer that remains after surgery.

Most radiotherapy treats cancer by directing beams of high energy X-rays at the tumour (although other radiation beams, such as gamma rays, electron beams or /heavy particle beams can also be used).

The X-rays interact with tumour cells, damaging their DNA and restricting their ability to reproduce. But because X-rays don't differentiate between cancerous and healthy cells, normal tissues can be damaged. Damaged healthy tissue can lead to minor symptoms such as fatigue, or, in rare cases, more serious outcomes such as hospitalisation and death.

Getting the right amount of radiation is a fine balance between therapy and harm. A common way to improve the benefit-to-cure ratio is to fire multiple beams at the tumour from different directions. If they overlap, they can maximise the damage to the tumour while minimising damage to healthy tissue.

How it works

Wilhelm Röntgen discovered X-rays in 1895 and within a year, the link between exposure to too much radiation and skin burns led scientists and doctors to pursue radiation in cancer treatment.

A single radiotherapy treatment takes 15 to 30 minutes. Credit: IAEA Imagebank/Flickr, CC BY

There are three key stages in the radiotherapy process. The patient is first imaged – using such machines as computer tomography (CT) or magnetic resonance imaging (MRI). This estimates the extent of the tumour and helps to understand where it is with respect to healthy tissues and other critical structures.

In the second stage, the doctor and treatment team will use these images and the patient's case history to plan where the radiation beams should be placed – to maximise the damage to the tumour while minimising it to healthy tissues. Complex computer simulations model the interactions of the radiation beams with the patient to give a best estimate of what will happen during treatment.

During the third, treatment-delivery stage, the patient lies still while the treatment beam rotates, delivering radiation from multiple angles.

Each treatment generally takes 15 to 30 minutes. Depending on the cancer and stage, there are between one and 40 individual treatments, typically one treatment a day. The patient cannot feel the radiation being delivered.

Benefits and side effects

Radiotherapy's targeting technology has made a significant difference to many cancers, in particular early-stage lung and prostate cancers. It is now possible to have effective, low toxicity treatments for these with one to five radiotherapy sessions.

For early-stage lung cancer studies estimate with radiotherapy, survival three years after diagnosis is at 95%. For prostate cancer, one study estimates survival at the five year mark is about 93%.

Side effects for radiotherapy vary markedly between treatment sites, cancer stages and individual patients. They are typically moderate but can be severe. A general side effect of radiotherapy is fatigue.

Other side effects include diarrhoea, appetite loss, dry mouth and difficulty swallowing for head and neck cancer radiotherapy, as well as incontinence and reduction in sexual function for pelvic radiotherapy.

Long-term effects of radiotherapy are a concern, particularly for children. For instance, radiation to treat childhood brain tumours can have long-lasting cognitive effects that can affect relationships and academic achievement.

Again doctors will need to weigh up the risks and benefits of treatment for individual patients. Proton beam therapy is arguably most beneficial in these cases.

Proton therapy requires large accelerators to give protons enough energy to penetrate deep into patients.

Other radiotherapy challenges

There are several challenges to current radiotherapy. It is often difficult to differentiate the tumour from healthy tissue, and even experts do not always agree on where exactly the tumour is.

Radiotherapy can't easily adapt to the complex changes in patients' anatomy when a patient moves – for instance, when they breathe, swallow, their heart beats or as they digest food. As a result, radiation beams can be off-target, missing the tumour and striking healthy tissue.

Also, we currently treat all parts of the tumour equally, despite knowing some of the tumour's regions are more aggressive, resistant to radiation and likely to spread to other parts of the body.

The tumour itself also changes in response to the treatment, further confounding the problem. An ideal radiotherapy solution would image and adapt the treatment continuously based on these changes.

Improvements in technology, including in imaging systems that can better find the tumour, can help overcome these challenges.

Proton beam therapy and other innovations

Proton beam therapy will help maximise benefits for many patients, including those with cancers near the spinal cord and pelvis. It requires large accelerators to give protons enough energy to penetrate deep into patients. The energetic protons are transported into the treatment room using complex steering magnets and directed to the tumour inside the patient.

Protons slow down and lose energy inside the patient, with most of the energy loss planned to occur in the tumour. This reduces energy loss in healthy tissues and reduces side effects.

The problems of changing patient anatomy and physiology in other forms of radiotherapy are also challenges for proton beam therapy.

Australia has a number of research teams tackling such challenges, including developing new radiation treatment devices, breathing aids for , measurement devices, shorter and more convenient treatment schedules and the optimal combination of with other treatments, such as chemotherapy and immunotherapy.

Explore further: Adaptive radiotherapy reduces pneumonitis while controlling lung cancer

Related Stories

Adaptive radiotherapy reduces pneumonitis while controlling lung cancer

May 5, 2017
Lung cancer patients who are treated with radiotherapy can develop an inflammation of the lung tissue called pneumonitis; this can limit the dose of radiation they can receive and severe forms of pneumonitis, if left untreated, ...

World-first in showing clinical-quality Proton CT for treatment of cancer

July 7, 2015
An international team of researchers will for the first time be able to demonstrate clinical-quality proton CT to improve proton therapy in the treatment of cancer – moving a step closer to this improved treatment method ...

Scientists put final pieces into place for seeing cancer with protons

December 1, 2015
Scientists are currently in South Africa putting together a unique medical imaging platform which could improve treatment for millions of cancer sufferers by making proton therapy a viable option.

Radiotherapy risks are much higher for smokers

March 20, 2017
Smokers treated for breast cancer have much higher risks than non-smokers of developing lung cancer or heart attack as a result of radiotherapy - according to a new study funded by Cancer Research UK and published today in ...

Researchers seek more effective radiotherapy treatment for cancer

July 1, 2014
A pioneering research project which aims to develop a more effective radiotherapy treatment for thousands of cancer sufferers will feature in a major public exhibition by The Royal Society.

New team to develop radiotherapies that target cancer more effectively

April 22, 2016
Safer precision radiotherapies that will be able to cure more cancers with fewer side-effects will be available within five years under ambitious new plans for research and treatment at the UCL Cancer Institute and University ...

Recommended for you

Researchers find adult stem cell characteristics in aggressive cancers from different tissues

September 19, 2018
UCLA researchers have discovered genetic similarities between the adult stem cells responsible for maintaining and repairing epithelial tissues—which line all of the organs and cavities inside the body—and the cells that ...

Ketogenic diet reduces body fat in women with ovarian or endometrial cancer

September 19, 2018
Women with ovarian or endometrial cancer who followed the ketogenic diet for 12 weeks lost more body fat and had lower insulin levels compared to those who followed the low-fat diet recommended by the American Cancer Society, ...

Eating foods with low nutritional quality ratings linked to cancer risk in large European cohort

September 18, 2018
The consumption of foods with higher scores on the British Food Standards Agency nutrient profiling system (FSAm-NPS), reflecting a lower nutritional quality, is associated with an increased risk of developing cancer, according ...

Could the zika virus fight the brain cancer that killed john McCain?

September 18, 2018
(HealthDay)—Preliminary research in mice suggests that the Zika virus might be turned from foe into friend—enlisted to curb deadly glioblastoma brain tumors.

CRISPR screen reveals new targets in more than half of all squamous cell carcinomas

September 18, 2018
A little p63 goes a long way in embryonic development—and flaws in p63 can result in birth defects like cleft palette, fused fingers or even missing limbs. But once this early work is done, p63 goes silent, sitting quietly ...

Enlarged genotype-phenotype correlation for a three-base pair deletion in neurofibromatosis type 1

September 18, 2018
International collaborative research led by Ludwine Messiaen, Ph.D., shows that while a three-base pair, in-frame deletion called p.Met992del in the NF1 gene has a mild phenotype for people with the genetic disorder neurofibromatosis ...

0 comments

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.