Paul Wheatley-Price ^1,2 Boaz Wong ^1,2 Hely Shah ¹ Harman Sekhon ³ Sara Moore ^1*

• ¹ The Ottawa Hospital, Ottawa, Ontario, Canada
• ² University of Ottawa, Ottawa, Ontario, Canada
• ³ Department of Pathology and Laboratory Medicine, The Ottawa Hospital, Ottawa, Ontario, Canada

Introduction: Aberrant expression of anaplastic lymphoma kinase (ALK) is found in 3-7% of patients with non-small cell lung cancer (NSCLC). Alectinib is a tyrosine kinase inhibitor used as first-line treatment targeting ALK-positive tumors. We herein report two cases of appendicitis highlighting it as a rare, possible adverse event of treatment with alectinib.Case presentation: The first case is a 60-year-old woman with a previous history of stage 1 lobular breast cancer and early-stage lung cancer treated with segmentectomy, subsequently presenting with ALK-positive advanced NSCLC. Treatment with alectinib resulted in partial response, but she developed gastrointestinal symptoms that were assessed with computed tomography (CT) of abdomen revealing right lower quadrant stranding without appendiceal visualization. Her symptoms continued despite antibiotic course with re-imaging concerning for acute appendicitis, which was successfully treated with appendectomy and amoxicillin-clavulanic acid. The second case is a previously healthy 58-year-old man with advanced ALK positive NSCLC who was started on first line treatment with alectinib and subsequently diagnosed with asymptomatic acute appendicitis on re-staging CT abdomen. Signs on CT resolved with amoxicillin-clavulanic acid.Definitive treatment was conducted with a delayed elective appendectomy. Both patients remained on alectinib over the courses of appendicitis without interruption. Conclusion: While appendicitis has not been previously described as an adverse effect of alectinib, its incidence in two patients at our center within several months following administration of alectinib raises its suspicion as a possible adverse effect.