Neoadjuvant crizotinib in ALK-rearranged inflammatory myofibroblastic tumor of the urinary bladder: A case report

INTRODUCTION: Inflammatory myofibroblastic tumor (IMT) is a rare mesenchymal tumor that involves various organs, but has a predilection for the urinary bladder in the genitourinary tract. Given that approximately half of all IMT cases have anaplastic lymphoma kinase (ALK) rearrangements, the ALK inhibitor crizotinib is suggested as a promising treatment for unresectable cases. No reports on neoadjuvant crizotinib therapy for locally advanced IMT of the bladder are available. PRESENTATION OF CASE: We report a case of a 17-year-old Japanese boy referred to our institution for painful urination and increased urinary frequency. He was diagnosed with ALK-positive IMT via transurethral resection of the bladder tumor. Computed tomography (CT) revealed a 5-cm mass and extramural invasion at the bladder dome. The diagnosis was locally advanced IMT of the bladder. We decided that partial cystectomy can be performed if neoadjuvant crizotinib therapy reduced the tumor size. After 2 months of administration, CT showed that the longest tumor diameter was reduced by 48%. Thus, we performed partial cystectomy, and the surgical margin was negative. No recurrence developed for over 1 year. DISCUSSION: IMT has intermediate malignant potential because its clinical course is relatively indolent with low risk of distant metastasis. As this patient is young and IMT of the bladder has good prognosis after surgical resection, bladder-preserving surgery is the most preferred approach. CONCLUSION: Neoadjuvant crizotinib therapy may be effective for large, locally advanced, and difficult to resect tumors.