UK Trial Will Test Proton Beam Therapy Versus Standard Radiation with Breast Cancer Patients

Radiation therapy is a key part of many breast cancer treatment plans, helping to minimize the risk of the disease returning. However, for a fraction of patients, this type of treatment can lead to heart issues later on, possibly more so if the patient had treatment on their left breast. A new trial aims to determine whether a more precise therapy may not impact the heart as much.

The PARABLE trial – led by researchers at the University of Cambridge, The Institute of Cancer Research, London, and the Royal Marsden NHS Foundation Trust – will compare proton beam therapy to standard radiation therapy for patients at higher risk of developing heart issues related to the treatment. Proton beam therapy can target radiation beams more precisely, so researchers aim to determine whether it can get sufficient radiation doses to breast tissue while sending less to the heart.


Professor Judith Bliss from The Institute of Cancer Research, says, “The PARABLE trial will measure average dose of radiotherapy delivered to the heart to predict long-term heart damage. Using this early predictor will allow us to uncover the potential benefits of using proton beam therapy for long term heart health in years rather than decades.”

The trial will involve 192 patients across the UK who are predicted to have at least a 2% lifetime risk of heart problems from radiation. According to the researchers, that would be about 500 out of every 30,000 breast cancer patients who receive standard radiation therapy. Each participant will receive either proton beam therapy or standard radiation.


The trial will measure radiation doses delivered to the heart, as well as have participants detail their experiences through questionnaires. The questions will address issues like skin reactions, breast pain and swelling, and other side effects from the treatment.

The team says that there are other countries where proton beam therapy is used as treatment, though not in large numbers, and this will be the first reported trial to directly compare it to standard radiation.

Dr. Anna Kirby, Breast Cancer Radiotherapy Team Lead at The Institute of Cancer Research and Radiotherapy Lead for the PARABLE trial, says, “We have already learnt a huge amount about how to optimise and standardise current breast cancer radiotherapy practices alongside optimising proton beam therapy approaches. We hope that the PARABLE trial will help us to further personalise radiotherapy treatments and ensure that people can access the radiotherapy approach that is best for them, regardless of where they live.”

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