15 / 06 / 21

Proton therapy – Present and future


Abstract

In principle, proton therapy offers a substantial clinical advantage over conventional photon therapy. This is because of the unique depth-dose characteristics of protons, which can be exploited to achieve significant reductions in normal tissue doses proximal and distal to the target volume. These may, in turn, allow escalation of tumor doses and greater sparing of normal tissues, thus potentially improving local control and survival while at the same time reducing toxicity and improving quality of life.

Protons, accelerated to therapeutic energies ranging from 70 to 250 MeV, typically with a cyclotron or a synchrotron, are transported to the treatment room where they enter the treatment head mounted on a rotating gantry. The initial thin beams of protons are spread laterally and longitudinally and shaped appropriately to deliver treatments. Spreading and shaping can be achieved by electro-mechanical means to treat the patients with “passively-scattered proton therapy” (PSPT) or using magnetic scanning of thin “beamlets” of protons of a sequence of initial energies. The latter technique can be used to treat patients with optimized intensity modulated proton therapy (IMPT), the most powerful proton modality.

Despite the high potential of proton therapy, the clinical evidence supporting the broad use of protons is mixed. It is generally acknowledged that proton therapy is safe, effective and recommended for many types of pediatric cancers, ocular melanomas, chordomas and chondrosarcomas. Although promising results have been and continue to be reported for many other types of cancers, they are based on small studies. Considering the high cost of establishing and operating proton therapy centers, questions have been raised about their cost effectiveness. General consensus is that there is a need to conduct randomized trials and/or collect outcomes data in multi-institutional registries to unequivocally demonstrate the advantage of protons.

Treatment planning and plan evaluation of PSPT and IMPT require special considerations compared to the processes used for photon treatment planning. The differences in techniques arise from the unique physical properties of protons but are also necessary because of the greater vulnerability of protons to uncertainties, especially from inter- and intra-fractional variations in anatomy. These factors must be considered in designing as well as evaluating treatment plans. In addition to anatomy variations, other sources of uncertainty in dose delivered to the patient include the approximations and assumptions of models used for computing dose distributions for planning of treatments. Furthermore, the relative biological effectiveness (RBE) of protons is simplistically assumed to have a constant value of 1.1. In reality, the RBE is variable and a complex function of the energy of protons, dose per fraction, tissue and cell type, end point, etc.

These uncertainties, approximations and current technological limitations of proton therapy may limit the achievement of its true potential. Ongoing research is aimed at better understanding the consequences of the various uncertainties on proton therapy and reducing the uncertainties through image-guidance, adaptive radiotherapy, further study of biological properties of protons and the development of novel dose computation and optimization methods. However, residual uncertainties will remain in spite of the best efforts. To increase the resilience of dose distributions in the face of uncertainties and improve our confidence in dose distributions seen on treatment plans, robust optimization techniques are being developed and implemented. We assert that, with such research, proton therapy will be a commonly applied radiotherapy modality for most types of solid cancers in the near future.

Mohan R, Grosshans D. Proton therapy - Present and future. Adv Drug Deliv Rev. 2017 Jan 15;109:26-44. doi: 10.1016/j.addr.2016.11.006. Epub 2016 Dec 3. PMID: 27919760; PMCID: PMC5303653.

*Please refer to the Terms and Conditions of this website when leaving the site and viewing third party content. 

Consultants we currently work with (proton therapy)

Prof Peter Barrett-Lee

Professor Peter Barrett-Lee is a Consultant Clinical Oncologist, Professor of Oncology in the School of Medicine at Cardiff University and...

Read more
Prof Peter Barrett-Lee

Dr Gaurav Kumar

Dr Gaurav Kumar received primary medical education and core oncology training from India. After working as a consultant in oncology...

Read more
Dr Gaurav Kumar

Prof John Staffurth

Professor John Staffurth is a Consultant Clinical Oncologist specialising in urological oncology. His clinical base is at Velindre Cancer Centre...

Read more
Prof John Staffurth

Dr Hans van der Voet

Dr Hans van der Voet is a senior consultant clinical oncologist and radiotherapy lead at the James Cook University Hospital...

Read more
Dr Hans van der Voet

Dr Eleanor Aynsley

Dr Aynsley graduated from Leeds Medical School in 1999. She did medical training in Durham, gaining MRCP in 2004. She...

Read more
Dr Eleanor Aynsley

Dr Cheng Boon

Dr Cheng Boon is Consultant Clinical Oncologist at the Worcester Oncology Centre at Worcester Royal Hospital. He completed medical training...

Read more
Dr Cheng Boon

Dr Kein Yim

Dr Kein Yim is a Consultant Clinical Oncologist. He undertook his medical training in the prestigious institutions of Edinburgh, Cambridge,...

Read more
Dr Kein Yim

Dr Sanjay Raj

Dr Sanjay Raj’s special interest is the treatment of breast cancer with chemotherapy, radiotherapy and biological and endocrine treatments. He...

Read more
Dr Sanjay Raj

Dr Christopher Herbert

Dr Chris Herbert qualified in medicine at Birmingham University in 2000. He trained in Clinical Oncology in Bristol and completed...

Read more
Dr Christopher Herbert

Dr Andrew Gaya

Dr Andrew Gaya is a consultant clinical specialist, who specialises in the multimodality treatment of gastroinstestinal cancers. Using a personalised...

Read more
Dr Andrew Gaya

Dr Shanmugasundaram Ramkumar

Dr Ramkumar is a Consultant Clinical Oncologist specialising in non-surgical treatment of Head and Neck cancer, Skull Base Tumours and...

Read more
Dr Shanmugasundaram Ramkumar

Dr Russell Banner

Dr Russell Banner is a Consultant Clinical Oncologist based in South Wales. His undergraduate training was at Christ’s College, Cambridge...

Read more
Dr Russell Banner

Dr Sanjana Masinghe

Dr Sanana Masinghe has been a consultant clinical oncologist at James Cook University Hospital, South Tees NHS Trust since 2016 and also...

Read more
Dr Sanjana Masinghe

Dr Muthiah Sivaramalingam

Dr Muthiah Sivaramalingam has been a consultant in Clinical Oncology since 2007 and has been Principal Investigator for many clinical...

Read more
Dr Muthiah Sivaramalingam

Dr Brinda Sethugavalar

Dr Brinda Sethugavalar studied primary medical education at the University of Dundee Medical School and obtained MBChB in 2004. She completed...

Read more
Dr Brinda Sethugavalar

Dr Jason Lester

Dr Jason Lester is a senior Consultant Clinical Oncologist based in South Wales. He trained and qualified in United Medical...

Read more
Dr Jason Lester

Dr Bart Kurec

Dr Bart Kurec is a consultant clinical oncologist in substantive post in Worcestershire Oncology Centre, specialising in the management of...

Read more
Dr Bart Kurec

Dr Rhian Davies

Dr Rhian Davies is a Consultant Clinical Oncologist specialising in the management of urological cancers. Her NHS post is in...

Read more
Dr Rhian Davies

Prof Amit Bahl

Professor Amit Bahl is a Consultant Clinical Oncologist and Clinical Director based at The Bristol Haematology & Oncology Centre, with a special...

Read more
Prof Amit Bahl

Dr Josef Kovarik

Dr Josef Kovarik is an acting consultant clinical oncologist and a Lead of ENT Oncology at the Northern Centre for Cancer...

Read more
Dr Josef Kovarik

Prof Roger Taylor

Professor Roger Taylor is a Consultant Clinical Oncologist specialising in the treatment of patients with brain tumours and lymphoma. Professor...

Read more
Prof Roger Taylor

Dr Esme Hill

Dr Esme Hill graduated from Birmingham University, also completing an Intercalated BSc in the History of Medicine at University College...

Read more
Dr Esme Hill

Dr Seema Arif

Dr Arif specialises in Gastrointestinal cancers (liver, pancreas, bile duct and bowel cancers). She graduated from India and completed post-graduate...

Read more
Dr Seema Arif

Dr Sarah Harris

Dr Sarah Harris qualified from King's College Hospital in 1989. She worked as Consultant Clinical Oncologist at Guys and St...

Read more
Dr Sarah Harris

Cancer treatments we offer

The Rutherford Cancer Centres provide high-quality cancer care by offering access to innovative and advanced treatment techniques using leading technology.

Consultants we work with

We provide exceptional patient support from diagnosis through to treatment and recovery, with leading consultants available at our centres across the country.

Centres across the UK

The Rutherford Cancer Centres provide cancer treatments and other healthcare services across the UK with our centres designed to put the patient experience first.

Contact Us

Get in Touch

If you'd like to speak to us about any of the treatments we offer please don’t hesitate to get in touch. Call us on 0800 210 0402 or

Our Trusted Healthcare Partners