Data Extraction and Risk of Bias Assessment

The senior author designed the data extraction sheet using Microsoft Excel. The sheet consisted of 3 different domains. The first one included the following items regarding both the study and included patients: the last name of the first author, the year of publication, the country where the study was conducted, the design of included study, the age and gender, and the characteristics of UTUC (i.e., history, location, and size) and MMC instillation (i.e., approach and maintenance). The second one included the main outcomes (efficacy and safety endpoints), as stated above. The third one included the quality domains that were assessed in each study using the Newcastle Ottawa Scale (NOS). Each study is therefore assessed at 3 levels: selection (4 points), comparability (2 points), and outcome (3 points). Both data extraction and quality assessment were performed by 2 authors, and the senior author was consulted whenever needed to solve any differences amongst authors.