Primary versus secondary muscle-invasive bladder cancer: survival after curative treatment

Purpose To assess if cancer-specific survival (CSS) following curative intent treatment (CIT) for muscle-invasive bladder cancer (MIBC) differs between patients presenting with MIBC (primary) and patients presenting with non-muscle-invasive bladder cancer who progress to MIBC (secondary). Methods This study uses data from the Cancer Registry of Norway on patients initially diagnosed with bladder cancer in 2008-2012 and treated with radical cystectomy (RC) or radiotherapy (RT). To ensure a clinically relevant population, we selected patients with a pre-treatment histology confirming muscle-invasion. Survival models were applied to evaluate differences in observed and adjusted CSS by type of MIBC and stratified by type of CIT. Adjustment was made for age group, sex, previous cancer, diagnostic hospital's academic status and geographical region, and type of CIT. Results We identified 650 eligible patients: 589 (91%) primary MIBC and 61 (9%) secondary MIBC. A total of 556 (86%) patients underwent RC and 94 (14%) RT. The 5-year CSS for primary MIBC was 56% and 59% for secondary MIBC (p = 0.68). The type of MIBC did not impact the risk of bladder cancer death (HR = 0.85, CI = 0.55-1.33, p = 0.48), nor when stratified for CIT (RC: HR = 0.93, CI = 0.57-1.53, p = 0.78); RT: HR = 0.71, CI = 0.24-2.16, p = 0.55). Conclusion This first nation-wide population-based study comparing CSS between primary and secondary MIBC showed no significant difference in survival regardless of type of CIT. Continued surveillance of patients with non-muscle-invasive bladder cancer is necessary to detect early progression to MIBC. Future studies should include molecular and genetic characteristics in addition to detailed clinicopathologic information.