Uterine Leiomyosarcoma with FN1-Anaplastic Lymphoma Kinase Fusion Responsive to Alectinib and Lorlatinib

Uterine leiomyosarcoma (LMS) is a rare malignant neoplasm of the female genital tract poorly responsive to conventional chemotherapy and radiotherapy, with an overall poor prognosis. Pazopanib is at the moment the only FDA-approved targeted molecular therapy for uterine LMS, given the exceedingly rare occurrence of actionable genetic mutations in this type of cancer. Here, we describe the first reported case of metastatic uterine LMS with an FN1-anaplastic lymphoma kinase (ALK) fusion mutation occurring in a 63-year-old woman with a history of uterine leiomyomas. The patient progressed on several lines of therapy, including conventional chemotherapy, pazopanib, and the first-generation ALK inhibitor crizotinib. Interestingly, the patient showed a remarkable 16-month response to second generation ALK inhibitors alectinib and lorlatinib. This case demonstrates that ALK inhibitors can be an effective therapeutic strategy for patients with ALK fusion-positive uterine LMS that has progressed on conventional chemotherapy.