Inflammatory Myofibroblastic Tumor of the Bladder With FN1-ALK Gene Fusion: Different Response to ALK Inhibition

Inflammatory myofibroblastic tumors are rare tumors with an ALK (anaplastic lymphoma kinase) gene rearrangement in up to 65% of all cases. In our patient, the tumor was not primary resectable due to its extension. Under neoadjuvant treatment with the first generation ALK inhibitor crizotinib no tumor response was seen, but the following therapy with the next generation ALK inhibitor lorlatinib led to a rapid and deep response, enabling a complete tumor resection by partial cystectomy. Our case indicates that ALK positive inflammatory myofibroblastic tumors which do not respond to ALK inhibition with crizotinib can be successfully treated with newer agents.