Short summary

The aim of this study is to assess the technical feasibility of delivering radical radiotherapy for prostate cancer using an MR-Linac. Acute and late GI and GU toxicity will also be assessed by physicians and using PROMS. 

Patients will be treated with 60 Gy/20 Fractions

PRISM-OUH is a standalone project within a large collaboration between the centres treating patients on MR-Linac. Each centre will be following this synchronised protocol to enable pooling of data at a later time. 

Rationale

Randomised trials have demonstrated that dose escalated radiotherapy improves outcome for prostate cancer patients. The use of increasingly conformal techniques, such as step and shoot IMRT (intensity modulated radiotherapy) or more recently VMAT (volumetric modulated arc therapy), has allowed this to be achieved while minimising associated increases in toxicity to surrounding normal structures. The accuracy of any radiotherapy delivery is, however, limited by multiple factors: organ delineation, set up error and inter-/intra-fraction organ motion, rotation and deformation. 

To allow safe dose escalation, the uncertainties in the treatment target must be mitigated using optimal planning and image-guided radiotherapy (IGRT). In particular, the increasing usage of profoundly hypo-fractionated stereotactic therapy is predicated on the ability to confidently direct treatment precisely to the intended target for the duration of each treatment. 

The use of increasingly sophisticated real time imaging has enabled monitoring of the prostate and OAR's through treatment delivery and has provided extensive data on their behaviour.  MRI, with its unrivalled soft tissue delineation, has contributed to this data but has not, as yet, emerged as a routine part of daily radiotherapy delivery. The long anticipated arrival of a fully integrated MR-Linac may change this.

The ideal scenario is to be able to adapt the radiotherapy plan to conform to the daily anatomy and to guide prostate radiotherapy using MR imaging also during radiation delivery. Such improvement in dose delivery accuracy may have the potential to improve the outcome.

Description of the cohort

Patients with prostate cancer stage T2-3a, N0,M0.