18 2011
IMAGING & ONCOLOGY
speCialised teams must be established with Creation of Consultant radiographer roles
development of national SBRT guidelines, training and research projects.
SERVICE DEVELOPMENT One of the barriers to implementation of SBRT is the lack of an appropriate tariff to recognise the extra planning effort required for this technique. How do we convince commissioners to ensure correct payment? Tariffs are based usually on number of treatment fractions rather than complexity of the planning and treatment process. The use of image guidance, for example, is not currently recognised within the tariff system. This issue has also been highlighted in the UK provision of inverse planned IMRT treatments13
. Mayles discusses
the need for financial recognition of the additional planning effort required for IMRT, an argument equally applicable to SBRT treatments. Unless a compensating increase in payment for the treatment preparation and data collection methods is implemented, it is unlikely that the desired level of SBRT provision will be achieved in the UK.
At a recent ‘Britain Against Cancer’ conference, the Health Secretary, Andrew Lansley, outlined plans to develop a range of tariffs to reward high-quality, cost-effective services14 help to encourage innovation and the early adoption of new techniques, such as SBRT.
. These may
The NRIG short term SBRT working party report (due early 2011) will provide guidance for commissioners, providers and clinicians for the provision of SBRT for all anatomical sites. It is anticipated the report will assist in solving this problem and enable more centres to offer this technique.
SBRT RESEARCH IN THE UK There is a vast number of published papers on SBRT, however there is a lack of level 1 evidence, with a striking absence of multicentre randomised controlled trials. Most of the literature on SBRT consists of cohort studies, phase I and a few phase II studies [15]. Radiobiology predicts that a high biological equivalent dose (≥100Gy) is needed for good local control (>80%)16
. Published outcomes from SBRT also support this, with dose/fractionation regimen delivering less than 100Gy being associated with poor local control17 . This observation
makes it difficult to randomise patients between the standard UK regimen of 55Gy/20 fraction (BED of 70Gy) against SBRT dose fractionation with a biologically equivalent dose higher than 100Gy. A couple of international phase III trials began in 2008, but are slow to recruit.
The number of stereotactic systems available in the UK with the facility for tumour tracking is expanding. The Cyberknife system provides continuous image guidance, target tracking and real time corrections. The Novalis Tx system provides marker based tumour tracking with gating techniques.
This does not mean that there is no place for research in SBRT. On the contrary, there are many unknowns. Even though local control rates are equivalent to surgery, this does not translate into a survival advantage. This phenomenon may be explained by the fact that patients selected for SBRT (over surgery) often have significant comorbidities, which may also affect their overall survival. Relapse patterns following SBRT differ significantly from conventional radiotherapy; with delivery of ablative doses, patients appear to relapse at distant sites with further treatment options limited, given that patients are usually medically inoperable. Both these factors could be responsible for the lack of survival advantage despite good local control.
Due to these factors, it is crucial that research in SBRT moves away from the medically inoperable. Certainly there are trials in Europe and America comparing SBRT to surgery, but due to the vastly differing trial arms they are slow to recruit18
. The UK Consortium
is also planning a trial of SBRT against surgery. A multicentre UK trial will help budding UK centres to start SBRT. In addition, the quality assurance associated with the trial will ensure best practice across centres delivering SBRT.
FUTURE IMPACT There is an increased body of evidence for the use of SBRT for oligometastases, liver, paraspinal, pancreas, prostate and kidney tumours2
. Some of these sites are already
being treated with SBRT in the UK. Each will have different issues to consider in terms of immobilisation, planning technique and image guidance. Further training may be required to evaluate the image guided images as the new sites may not be currently treated using radiotherapy and soft tissue matching.
As all new linacs are recommended to be capable of delivering image guided 4D adaptive radiotherapy19 treatments.
, this gives the potential for an increased number of SBRT
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