A case of lupus anticoagulant induced by bevacizumab targeted therapy after lung cancer surgery

Background: Lupus anticoagulant (LA) testing is a key component of laboratory detection for antiphospholipid antibodies, primarily used for diagnosing antiphospholipid syndrome (APS) and systemic lupus erythematosus (SLE) ^[1,2] , assessing venous thromboembolism (VTE) risk ^[3] , and investigating unexplained prolonged activated partial thromboplastin time (APTT). Bevacizumab, a recombinant humanized monoclonal IgG1 antibody targeting vascular endothelial growth factor (VEGF), is widely used in various cancers, including non-small cell lung cancer (NSCLC) ^[4,5] . To date, no report has described bevacizumab-induced LA in lung cancer patients. Case presentation: A 54-year-old male received cisplatin/pemetrexed chemotherapy combined with bevacizumab targeted therapy (every 21 days) for one year after lung cancer surgery. APTT remained normal throughout treatment and early post-operative period. In July 2025, during hospitalization for thyroid nodules, marked APTT prolongation was incidentally found. APTT mixing studies indicated the presence of an inhibitor. LA testing was positive (LA ratio 1.62, rising to 1.82 ten days later), while coagulation factors VIII, IX, XI, XII activities, factor VIII antibody, antinuclear antibody profile, anticardiolipin antibodies, and anti-β2-glycoprotein I antibodies were all negative. After withholding one dose of bevacizumab, APTT and LA levels decreased significantly (LA ratio 1.39). The patient underwent uneventful thyroid surgery. Upon resuming bevacizumab, APTT prolonged again and LA increased (LA ratio 1.75). The patient had a 20-year history of clozapine use, but APTT was normal before lung cancer surgery, ruling out clozapine as the cause. Conclusion: This is the first report of bevacizumab targeted therapy potentially inducing LA production in a lung cancer patient. The mechanism may involve VEGF inhibition leading to vascular endothelial injury, exposure of subendothelial phospholipids, and subsequent immune activation producing antiphospholipid antibodies. Clinicians should consider LA testing when encountering unexplained APTT prolongation in patients receiving bevacizumab, to accurately assess thrombotic risk and avoid misdiagnosis.