First UK proton beam therapy trial launches for certain breast cancer patients

The first UK trial to evaluate the benefits of proton beam therapy in certain patients with breast cancer has been launched.

The therapy, which can target radiotherapy beams more precisely, will be compared with standard radiotherapy in patients who are at greater risk of long-term heart problems after radiotherapy treatment.

The PARABLE trial, which will enrol 192 patients across 22 planned sites in the UK, will be led by researchers at the University of Cambridge, the Institute of Cancer Research, London (ICR) and the Royal Marsden NHS Foundation Trust, and funded by a National Institute for Health and Care Research and Medical Research Council partnership.

Standard breast cancer radiotherapy is very effective for the vast majority of patients. However, for a small group, there is a risk of heart problems later in life due to breast radiotherapy.

This is usually because their breast tissue and the lymph nodes that require radiotherapy treatment are located close to the heart, or because they have an increased underlying risk of developing heart problems later in life.

Unlike standard radiotherapy however, which uses high energy x-rays to kill cancer cells, proton beam therapy uses charged particles to target tumours more precisely.

Researchers hope that using the therapy for these patients will allow doctors to deliver adequate doses of radiotherapy to breast tissue, while minimising off-target radiation delivered to the heart.

Patients who are predicted to have at least a 2% or higher potential lifetime risk of heart problems from radiotherapy will be invited to take part in the trial.

Professor Judith Bliss, director of the Cancer Research UK-funded clinical trials and statistics unit at the ICR, which is managing the PARABLE trial, said: “We’re delighted to launch the PARABLE trial to put proton beam therapy to the test and determine whether it has benefits over standard radiotherapy in a group of people who may need more targeted treatment.

“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.”

Patients will also record their experiences using questionnaires so that researchers can assess side-effects including skin reactions, breast pain and swelling.