10 2011


IMAGING & ONCOLOGY


therapy. An expert reference panel receives patient referrals for treatment abroad at one of three centres: the Paul Scherrer Institute, Villigen, Switzerland; the Centre- Protontherapie, Orsay, France; or the University of Florida Proton Therapy Institute, Jacksonville, USA. This national service has been available since April 2008 and has resulted in more than 70 UK patients being treated overseas. Although providing a necessary and important clinical service, treatment abroad for several weeks can provide significant challenges for patients and their carers.


There is a clear emphasis on the treatment of paediatric patients in the current list of approved diagnoses, with an expected patient benefit from the reduction in the integral dose delivered for this group. The UK population receiving proton radiotherapy therefore has a significantly different profile from the international standard, with approximately a quarter of patients receiving proton radiotherapy presenting with prostate cancer2 the USA, prostate cancer patients are the predominant referral for proton radiotherapy.


. In


The treatment of patients abroad provides a service only for those who will benefit most from this form of treatment. However, in its current form, the number of patients receiving this form of radiotherapy is unlikely to meet fully the UK demand. An early estimate of the number of patients that could benefit from proton radiotherapy in England alone is in excess of 1700 cases per annum3


. Treating this number of patients


at facilities overseas would be a significant logistical challenge associated with substantial costs. It is therefore highly likely that UK based proton radiotherapy facilities will be required in the next five years.


CLINICAL AND COST-EFFECTIVENESS OF PROTON RADIOTHERAPY Opponents of proton radiotherapy often point to a lack of clinical evidence and the high relative cost of the treatment facilities to question the need for proton radiotherapy in the UK. Systematic reviews are unlikely to provide any definite answers on the effectiveness of proton radiotherapy for a number of reasons: The lack of good quality randomised trials; the lack of comparative studies in general; the use of different definitions of acute and late effects of treatment; and the emphasis on single institution reported series of proton only treatments. What is clear is that proton radiotherapy provides distinct dosimetric advantages over photon treatments, including IMRT, in terms of reduced dose to normal tissues, particularly distant to the tumour4 reduction in normal tissue dose may provide the potential for dose escalation, or


. This The major hindrance to the greater use of proton radiotherapy centres is the substantial


signifiCant investment instaff training is required


morbidity reduction for patients receiving proton radiotherapy.


Ultimately, the clinical effectiveness of proton treatment must be demonstrated by clinical trials. However, one difficulty in this approach is that the main difference between proton and photon radiotherapy dose distributions lies in the low to medium radiation dose range delivered to the patient, with protons affecting smaller volumes of healthy tissues in this range. This difference is likely to be demonstrated clinically in the late effects of radiotherapy treatment, whose frequency can be difficult to measure and requires lengthy follow-up of the patients. The length of follow-up negates the ability of clinical trials to guide health policy in the short term.


As discussed by Zeitman et al5 , even those opposed to proton radiotherapy in


general, accept that their application to paediatric tumours is desirable, if not clinically proven, and should be supported without further proof. This is due to the fact that normal tissues in a growing child are particularly radiosensitive and the morbidity from conventional radiotherapy treatments can be substantial. The demonstrated improvements in the dose distribution by proton radiotherapy are highly likely to be advantageous for this patient group. Given the high cost of proton radiotherapy, it should perhaps be reserved for patients in whom great benefits over best quality photon radiotherapy are to be expected.


DRIVERS FOR TECHNOLOGICAL CHANGE One of the most important areas of progress for proton radiotherapy is the ongoing development of technology. It is well known that proton radiotherapy treats far fewer patients than photon based radiotherapy and that commercially, proton radiotherapy is a much smaller worldwide market. As a result, proton radiotherapy equipment is currently less mature. However, since proton radiotherapy moved from the realm of the particle physics laboratory to dedicated clinical facilities either attached or affiliated to hospitals, the uptake of proton radiotherapy has accelerated and, along with it, the interest in developing improved technology and integrated solutions. The result is that compared to photon based radiotherapy, proton radiotherapy technology will undergo major developmental changes over the next few years.


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