Radiotherapy for BCG-unresponsive Non-muscle-invasive Carcinoma in Situ (CIS) Bladder Cancer: an Open-label, Single-arm, Multicentre, Phase 2 Study

Standard treatment for patients with high-risk NMIBC (high-grade Ta, CIS, or any T1) consists of intravesical Bacillus Calmette-Guerin (BCG) immunotherapy. However, BCG, even administered optimally, does not provide absolute protection and BCG failure is generally considered recurrence or progression during therapy. Patients who are BCG-unresponsive have a 20-40% risk for progression to muscle-invasive bladder cancer within 5 years, and a 50% risk of developing metastatic disease. For these patients, radical cystectomy with pelvic lymph node dissection and urinary diversion is the standard of care. However, many patients are unable to undergo radical cystectomy because of poor performance status and co-morbidities or decline to undergo surgery. Although, several phase II studies have shown promising results, none of the drugs are presently available in Europe. An alternative approach is to investigate a possible role for radiotherapy in good prognosis bladder cancer patients. As there is little existing data in NMIBC, the example of bladder preservation in MIBC will be used for guidance. We aim to evaluate the use of radiotherapy in patients with high-grade non-muscle-invasive bladder cancer who have BCG failure in a single-arm design as per FDA guidelines for this setting. The primary objective is to demonstrate that complete response to treatment 6 months post radiotherapy is seen in more than 30% of patients with BCG-unresponsive, non-muscle invasive carcinoma in situ bladder cancer, unfit or unwilling to undergo radical cystectomy. Patients with BCG unresponsive non-muscle-invasive bladder cancer according to the EAU guidelines will be treated 20 fractions of 2.75 Gy over 4 weeks with the use of radiosensitisers as per local guidelines. Cystoscopy and urine cytology assessments will be performed at 3 and 6 months from the start of radiotherapy. If either assessment is positive, bladder biopsies or TURBT are required. At the 6-month timepoint, biopsy or TURBT is mandatory. Disease assessments beyond 6 months will be at the treating urologist's discretion.