Radiotherapy for BCG-unresponsive Non-muscle-invasive Carcinoma in Situ (CIS) Bladder Cancer

Inclusion Criteria: * 18 years or older with histologically confirmed, BCG-unresponsive, high-risk non-muscle-invasive bladder cancer of predominantly (\>50%) urothelial histology who were ineligible for or declined to undergo radical cystectomy * Patients with carcinoma in situ with or without high-grade Ta or T1 * Eastern Cooperative Oncology Group performance status of 0-2, and adequate organ function * Patients with concomitant Ta and T1 tumours must have undergone complete TURBT, defined as per standard of care as a visually complete resection (residual carcinoma in situ, which is traditionally not amenable to complete transurethral resection is acceptable), and the most recent cystoscopy or TURBT must have been done within 12 weeks before study initiation. Presence of detrusor muscle on pathology samples is required to ensure sample adequacy. A second TURBT is recommended but not required for patients with T1 tumours. The use of either white-light cystoscopy or blue-light cystoscopy is permitted, but the same technique has to be used in a patient throughout the trial * Definition of BCG unresponsive non-muscle-invasive bladder cancer according to the European Association of Urology (EAU) guidelines Exclusion Criteria: * Evidence of upper urinary tract carcinoma * Hydronephrosis due to tumour in the presence of T1 disease * Patients on current systemic therapy for bladder cancer * Patients who have received pelvic external beam radiotherapy within the previous 5 years