Partial Response to Treatment with ALK Inhibitor in a Patient With SQSTM1-ALK Fusion Positive Lung Adenocarcinoma.

Introduction: Lung cancer is the second most common cancer worldwide and the leading cause of cancer deaths; non-small cell lung cancer (NSCLC) constitutes about 85% of lung cancer cases, with ALK fusions representing 3-6% of them. The SQSTM1-ALK fusion is a rare finding in NSCLC, accounting for only 1.1% of ALK rearrangements. We present a case of lung adenocarcinoma with documentation of SQSTM1-ALK fusion that showed a partial response to alectinib. Case description: This case details the clinical course of a 71-year-old, non-smoking woman with no significant medical history who presented with confusion, aphasia and multiple cerebral lesions detected on imaging. Further investigations revealed a stage IV lung adenocarcinoma with metastases to the brain and adrenal gland. Molecular profiling identified a rare SQSTM1-ALK fusion mutation alongside other genetic abnormalities, including low programmed death-ligand 1 expression and ROS1 kinase protein presence. Treatment with alectinib, initiated based on the identified ALK fusion, resulted in significant tumour regression in the lungs and complete resolution of the adrenal mass, as evidenced by follow-up imaging and clinical assessments. Conclusion: This case highlights the efficacy of alectinib in treating rare ALK fusion variants in and underscores the importance of comprehensive molecular profiling in guiding targeted therapy decisions. LEARNING POINTS: