UCLH and UCL researchers trial proton beam therapy in bid to transform treatment for mesothelioma

Clinician researchers at UCLH and UCL are leading a major UK clinical trial to test whether proton beam therapy (PBT) can significantly improve survival for patients with mesothelioma, a rare and aggressive cancer of the lining of the lung.

The HIT-MESO trial is the first randomised clinical trial in the UK to investigate proton beam therapy for mesothelioma. Researchers hope the treatment could increase two-year survival rates from around 30% to 50%, potentially reshaping national treatment guidelines.

Mesothelioma is usually caused by asbestos exposure and most commonly affects the lining around the lungs (pleural mesothelioma). More than 2,700 people are diagnosed in the UK each year, predominantly older men. There is currently no cure, and treatment options are limited, with overall survival rates remaining poor.

Standard radiotherapy can help control small areas of mesothelioma, such as painful tumours, but is not usually suitable for treating the full lining of the lung, where the disease spreads. Treating such a large area with conventional radiotherapy risks damaging vital organs including the heart, lungs and liver, leading to serious side effects.

Proton beam therapy uses targeted beams of protons that deposit most of their energy directly in the tumour, minimising radiation exposure to surrounding healthy tissue. For mesothelioma, this approach could dramatically reduce radiation to critical organs, potentially allowing more effective treatment with fewer side effects.

Dr Crispin Hiley, chief investigator of the HIT-MESO trial, UCLH consultant oncologist and associate professor at the UCL Cancer Institute said: “Mesothelioma is one of the most challenging cancers we treat. Conventional radiotherapy simply cannot safely cover the full area affected by the disease without causing unacceptable harm to healthy tissue.

“Proton beam therapy allows us to deliver high-dose radiation far more precisely, sparing critical organs like the heart and healthy lung. Through this trial, we hope to show that this approach can significantly improve survival and quality of life for patients. If successful, it could fundamentally change how mesothelioma is treated in the UK.”

The HIT-MESO trial aims to recruit up to 148 patients from 23 NHS centres across England and Wales. Participants receive daily proton beam therapy, Monday to Friday, for five weeks, at either UCLH or The Christie NHS Foundation Trust in Manchester. Around 50 patients have already been recruited.

The trial, which is supported by the National Institute for Health and Care Research (NIHR) UCLH Biomedical Research Centre and the NIHR North London Regional Research Delivery Network, and delivered by the UCLH Cancer Clinical Trials Unit, is open to patients whose mesothelioma is confined to the lining of one lung and who have not yet received anti-cancer treatment.

One of the patients taking part is Peter Littlefield, 83, from Portsmouth, who was diagnosed with mesothelioma last autumn after developing a persistent cough and breathlessness.

Peter said: “When they told me I had cancer, I felt shocked, of course, but almost straight away I went into practical mode: right, let’s deal with it.

“Surgery wasn’t an option, and neither chemotherapy nor standard radiotherapy would be effective, but when they mentioned this trial using proton beam therapy, I said yes immediately. Being accepted was the best Christmas present I could have hoped for.

“I don’t know how I’ll respond, but I’m hopeful. If it can slow things down, give me more time, and help me stay active, that’s what matters most to me. I’m not ready to sit still, and I’m certainly not ready to give up.”

An active outdoorsman who enjoys fishing and shooting, Peter is determined to remain mobile and positive throughout his treatment. He and his wife travelled to London for five weeks to get proton beam therapy, supported by his local NHS team at Portsmouth University Hospital led by consultant clinical oncologist Dr Hannah Bainbridge.

If successful, the HIT-MESO trial could lead to proton beam therapy becoming a new standard treatment for selected mesothelioma patients, offering improved survival and better quality of life.

Dr Hiley added: “This trial represents a major step forward for patients who currently have very limited options. Our goal is not just to help people live longer, but to live better.”

Dr Samantha Walker, Director of Research and Innovation at Asthma + Lung UK, which is funding the trial, said: “Asthma + Lung UK is proud to be funding this vital research, which has the potential to improve quality of life and prolong the lives of people with mesothelioma. With life expectancy remaining low and no current cure available, progress on the treatment of this devastating condition is desperately needed – this study could be a real breakthrough.  

“Proton radiotherapy has already shown promising potential for other types of cancer. If this trial is successful, it would offer new hope for the more than 2,000 people who are diagnosed with mesothelioma every year, highlighting the importance of research into new types of treatment. Yet we know current funding for lung health research is on life-support, despite lung conditions remaining the third biggest cause of death in the UK – this urgently needs to change.”