The risk of a venous thrombotic event in lung cancer patients: higher risk for adenocarcinoma than squamous cell carcinoma

Summary Background: Only limited data on the incidence of venous thrombosis in different types of malignancy are available. Patients with adenocarcinoma are believed to have the highest risk of developing venous thrombosis. Objectives: To study the incidence of thrombosis in patients with lung cancer, with an emphasis on the comparison between adenocarcinoma and squamous cell carcinoma, we have performed a cohort study of patients with non‐small‐cell lung cancer. In addition the risk associated with treatment and extent of disease was assessed. Patients/methods: A total of 537 patients with a first diagnosis of lung carcinoma were included. Patient and tumor characteristics as well as venous thrombotic events were recorded from the medical records and from the Anticoagulation Clinic. Results: Thrombotic risk in lung cancer patients was 20‐fold higher than in the general population (standardized morbidity ratio (SMR): 20.0 (14.6–27.4). In the group of patients with squamous cell cancer we found 10 (10/258) cases (incidence: 21.2 per 1000 years) of venous thrombosis whereas in the group of patients with adenocarcinoma 14 (14/133) cases (incidence: 66.7 per 1000 years) occured. The crude adjusted hazard ratio was 3.1 (95% CI: 1.4–6.9). The risk increased during chemotherapy and radiotherapy and in the presence of metastases. Conclusions: The risk of venous thrombosis in lung cancer patients is increased 20‐fold compared to the general population. Patients with adenocarcinoma have a higher risk than patients squamous cell carcinoma. During chemotherapy or radiotherapy and in the presence of metastases the risk is even higher.