BCG-itis incidence and seriousness among patients treated with intravesical BCG

<bold>Introduction:</bold> For nearly five decades, immunotherapy with intra-vesical Bacillus Calmette-Guérin (BCG) has been a used for treating non-muscle invasive bladder cancer. This study aims to assess the frequency and severity of complications arising from BCG therapy, referred to as BCG-itis. Additionally, we are looking to analyze factors potentially linked to these complications, with a particular focus on investigating any suspected increase in their incidence. <bold>Methods:</bold> Between January 2019 And December 2023, all patients treated with BCG from the region of Zealand in Denmark (population of 840,000) were analyzed for yearly incidences of systemic BCG-itis (BCG-SI) or localized BCG-itis (BCG-LI), using electronic medical record data search including also ICD-10 of tuberculosis infection / disease and ATC-code of isoniazide. We used descriptive statistics, chi-square and multivariate analyses. <bold>Results:</bold> Overall, the mean number of BCG instillations /patient was 4650/685=6.8, and for each of the yearly periods was 1424/243=5.9 (2019), 631/148=4.3 (2020); 659/149=4.4 (2021); 815/214=3.8 (2022); 1130/220=5.1 (2023). The proportions of treated BCG-SI in each period were 0/376=0%; 0/149=0%; 0/214=0%; 7/220=3%; respectively. The BCG-LI proportions were 5/376=1.3%; 1/149=0.7%; 1/214=0.5%; 4/220=1.8%. Further analyses are planned to identify significantly associated co-factors. <bold>Conclusion:</bold> In this population from 2019 to 2023, the often severe BCG-SI episodes (in our case ophtalmologic, pulmonary, BCG-sepsis) increased abruptly from zero to 3% in the last year. Further analyses for possible significant cofactor associations are on-going.