Background With indications for immune checkpoint inhibitor (ICI) therapy steadily growing, immune related adverse events (irAEs) are increasingly common in the oncologists’ practice. In the absence of prospective irAE management trials, the currently existing guidelines on irAE treatment are based on case series, retrospective reviews, and expert opinion. As some of the most lethal irAEs (like pneumonitis, myocarditis, or encephalitis) are rare, multidisciplinary collaboration and discussion is essential. Many countries have responded to this challenge by organizing regional immunotoxicity boards.^{1 2} Belgium is unique in that it has a nationwide virtual board meeting, serving more than 300 Belgian oncologists.

Methods BITOX is a biweekly virtual meeting between oncologists and organ specialists accessible to all Belgian hospitals.³ Questions regarding diagnosis, management, and prevention of irAEs are submitted online. During the meetings, diagnostic and therapeutic suggestions are made and communicated to the treating physician. The aim is to share experiences, standardize the approach for irAEs and identify clinically relevant research questions.

Results Since its creation in March 2021, 164 cases were discussed. The majority (n=110; 67%) are questions regarding irAE differential diagnosis and management. Despite their absolute rarity, neurological irAEs are most frequently discussed (n=15; 14%), which stresses the unmet medical need in this area. The other questions (33%) deal with the safety of (re)starting ICI therapy in patients with dysimmune comorbidities. These comorbidities are autoimmune diseases (n=23; 43%), a history of irAE (n=21; 39%), transplant (n=5; 9%) and rarer hematological diseases or paraneoplastic syndromes. We receive questions from university hospitals (n=73; 48%) as well as general hospitals (n=79; 52%) and from both medical oncologists (n=118; 76%) and organ specialists (24%). Cases from 81 different health care practitioners were discussed, concerning patients from 39 different Belgian hospitals on both sides of the language border. Up to 33% of physicians submit a case more than once, illustrating the easy accessibility of the board. We have seen a steady increase in weekly submissions over the last two years with an average of 14 cases per quartile in 2021, 17 in 2022, and 20 in 2023.

Conclusions The Belgian national multidisciplinary immunotoxicity board aims to harmonize irAE treatment in Belgium. Its unique nationwide reach is an excellent position to identify clinically relevant research questions, which has led to the development of the IMPROVE concept, a prospective irAE management trial framework, with its first trial focusing on immune related pneumonitis treatment expected to start mid 2024.

Acknowledgements We would like to thank the BSMO immuno taskforce for their valuable and ongoing contributions.

References

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2. Naidoo J, Zhang J, Lipson EJ, Forde PM, Suresh K, Moseley KF, Mehta S, Kwatra SG, Parian AM, Kim AK, Probasco JC, Rouf R, Thorne JE, Shanbhag S, Riemer J, Shah AA, Pardoll DM, Bingham CO, Brahmer JR, Cappelli LC. A Multidisciplinary Toxicity Team for Cancer Immunotherapy-Related Adverse Events. J Natl Compr Canc Netw. 2019;17(6):712–720.

3. Verhaert M, Aspeslagh S, Bechter O, Wuyts S, Blockx N, Brandao M, Dekervel J, Neyns B, Rutten A, Seront E, Wauters E, Schreuer MS, Drowart A. The Belgian Multidisciplinary Immunotoxicity Board (BITOX): A nationwide initiative of the Belgian Society of Medical Oncology (BSMO). Ann Oncol. 2021;32:S1405.