Study of Weekly Radiotherapy for Bladder Cancer (HYBRID)

Background Localised muscle invasive bladder cancer (MIBC) is life-threatening and can cause significant symptoms. Around 50% of patients with MIBC who are referred for radiotherapy are unfit for standard radical treatment (surgery or daily radiotherapy with chemotherapy), but would have a normal life expectancy if their cancer were adequately controlled. Retrospective studies suggest that radiotherapy which is given weekly using fewer fractions and higher doses (hypofractionated), may be an alternative where daily radiotherapy is not an option.

Radiotherapy treatment is planned based on information from a CT scan which shows the position and shape of the bladder. This plan needs to take into account the fact that the bladder's shape and position can change, depending on how full it is and because of where it is in relation to the bowel. A safety margin is therefore added around the bladder on the planned treatment, to reduce the risk of missing any of the bladder with the radiotherapy.

It is now possible to take scans of the bladder's position before each treatment and adjust the position of the treatment plan accordingly to ensure the bladder is fully covered by it. In this study we are also looking at whether it is possible to design a series of treatment plans with different size safety margins and then choose one that fits best for each particular day. This is called 'adaptive radiotherapy'. This technique may enable accurate treatment delivery using smaller safety margins and this might help to reduce side effects.

Aims

In patients with MIBC not suitable for cystectomy or daily radiotherapy we aim to assess:

1. whether treatment using adaptive planning can be successfully delivered at multiple sites across the UK and results in acceptable levels of toxicity
2. the local tumour control rate achieved by hypofractionated weekly radiotherapy
3. the requirement to treat with adaptive planning.

How results will be used Results will provide robust evidence for use of hypofractionated radiotherapy and assess whether this is a plausible and worthwhile treatment in this patient population. The randomised element of the trial will support the implementation of image-guided adaptive radiotherapy for bladder cancer in the UK. HYBRID will provide evidence on the benefits or otherwise of this methodology and inform the development of further trials in this and other patient groups.