Cystectomy/*methods Humans Organ Sparing Treatments/*methods Treatment Outcome Urinary Bladder Neoplasms/*surgery Bladder preservation High-grade non-muscle-invasive bladder cancer Meta-analysis Radical cystectomy PUBLICATION: Not applicable. COMPETING INTERESTS: The authors declare that they have no competing interests. PUBLISHER’S NOTE: Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.