Excellent response of lung adenocarcinoma harboring a rare SLC8A1 downstream intergenic region ALK fusion to ceritinib treatment: A case report

Rationale: Anaplastic lymphoma kinase (ALK) gene fusion, an important driver gene alteration leading to the development of lung cancer, occurs in 5% of nonsmall cell lung cancer (NSCLC) cases in China. In addition to echinoderm microtubule-associated protein-like 4 (EML4)-ALK, which is the most common type of ALK fusion, various fusion partner genes have been identified in recent years. However, ALK intergenic breakpoint fusions confound fusion detection and targeted treatment. Patient concerns: A 40-year-old woman presented to our hospital with a 2-month history of a cough. Diagnosis: Based on the right hilar lymph node biopsy and positron emission tomography computed tomography (PET-CT) examination, the patient was diagnosed with "stage IV lung adenocarcinoma" showing metastases in the mediastina, right hilar lymph nodes, and C7 vertebral body. A rare solute carrier family 8 member A1 (SLC8A1) downstream intergenic region ALK fusion was identified in biopsy specimens using next-generation sequencing (NGS). Interventions: The patient received first-line molecular-targeted therapy (ceritinib). Outcomes: After nearly 9 months, the best evaluation of partial remission (PR) was obtained. Lessons: This is the first clinical evidence of advanced NSCLC due to a rare SLC8A1 downstream intergenic region ALK fusion that has been effectively treated with ceritinib. Whether this finding represents an inherent property of this fusion protein or its unique clinicopathological characteristics in patients carrying this fusion protein remains to be investigated. Moreover, the patient's durable response to ceritinib and future resistance mechanisms require further follow-up.