Pembrolizumab in Muscle Invasive/Metastatic Bladder Cancer

PLUMMB is an phase I trial to investigate the safety, tolerability and effectiveness of an immunotherapy drug called Pembrolizumab used in combination with radiotherapy. The study will also investigate two different doses of pembrolizumab, starting at 100mg (through an intravenous drip) and increasing to 200mg for the next cohort of patients, if the first dose is well tolerated. The patients suitable for this study will be: Group A those with locally advanced bladder cancer or Group B patients whose cancer has spread from the bladder (metastatic bladder cancer). Treatment in the PLUMMB trial will start with a pembrolizumab 2 weeks prior to starting a course of 4 - 6 weeks radiotherapy. Treatment with pembrolizumab will then be given every three weeks. Patients in Group A will then continue to take pembrolizumab for up to a year unless they have disease progression or unacceptable side effects in the meantime. Patients in Group B will continue taking pembrolizumab for as long as needed until they have disease progression or unacceptable side effects. Patients will be seen every 3 weeks during treatment and every 3-6 months thereafter. CT scans will be done every 3 months during treatment and as per usual care (usually 6 monthly) after the treatment has finished. Patients in Group A will also have a cystoscopy (camera test) to look into the bladder 3 months after they finish radiotherapy. This is standard care and would be the same for patients not on a research study.