Background: Historically, extensively drug-resistant tuberculosis (XDR-TB) has been notoriously difficult to treat resulting in devasting outcomes. As we are coming to the end of an era where the 2006 XDR-TB definitions and old treatment regimens are being replaced, we aimed to estimate the proportion of XDR-TB patients globally who achieved successful treatment outcomes.

Methods: We searched PubMed/MEDLINE, Scopus, Web of Science, and Embase from January 1, 2005, through April 3, 2023. Included studies reported WHO treatment outcomes, or adaptions hereof, for pre-XDR and/or XDR-TB patients according to the 2006 WHO definition. Eligible studies included cohorts of at least 10 adults (aged >18 years) that were not pregnant. Using a random-effects model, we calculated pooled proportions of treatment outcomes and performed sensitivity and subgroup analyses.

Results: Among 5,056 studies reviewed, we identified 94 studies from 26 countries, involving 10,223 XDR-TB patients. The pooled proportion of successful treatment outcomes was 44.2% (95%CI: 38.3-50.3). Sensitivity analyses consistently produced similar estimates. A slight improvement in treatment outcomes was observed after 2013. Furthermore, 25 studies reported outcomes for 3,564 individuals with pre-XDR-TB, of which 63.3% achieved successful treatment (95%CI: 43.1-72.5). 

Conclusion: Globally, the success rate of XDR-TB treatment is 44.2%, far below the WHO?s target rate of 75%. These results may serve as a reference for future studies assessing XDR-TB treatment outcomes under the 2021 definition treated with novel and better treatment regimens.