Incidence and Risk Factors for Thrombosis in Cancer Patients with COVID-19

Introduction: Cancer is a leading cause of morbidity and mortality in the United States, and cancer patients infected with COVID-19 are at increased risk of death. Given that cancer and COVID-19 are both risk factors for thrombosis, it has been hypothesized that cancer patients with COVID-19 may be at greater risk for thromboembolic events than patients with COVID-19 alone. This risk could necessitate the need for more vigilant thrombosis prophylaxis. However, studies investigating risk factors for thromboembolic events in this population are limited with mixed results. We aimed to determine the incidence and risk factors for thromboembolic events in patients with cancer and COVID-19.

Methods: We performed a retrospective cohort review of all cancer patients hospitalized with COVID-19 at our institution between January 1, 2021 and April 1, 2023. Patients over the age of 18 who had previously been diagnosed with cancer, received treatment within the prior 6 months, and had been hospitalized due to COVID-19 were included in the study. We assessed whether patients had experienced a thromboembolic event during their hospital stay, which included thrombosis of the extracorporeal circuit, distal or proximal lower extremity deep venous thrombosis (DVT), upper extremity DVT, pulmonary embolism, superficial thrombophlebitis, ischemic stroke, or other arterial event. Information regarding comorbidities and clinical course was extracted from the patient's record. Descriptive analysis was performed, and association between qualitative variables was studied with the Chi-squared test and the Fisher Exact test, when appropriate. For quantitative variables, the t-test or the Mann-Whitney U test was performed. Multivariate logistic regression was used to assess variables predictive of thromboembolic events.

Results: 456 patients with cancer and COVID-19 were included in the study. The median age was 69 years (IQR 62 - 78) and 55% of patients were male. The majority (85%) of patients were White. Most patients had either lung (19%) or bone marrow (17%) cancer, and 196 (43%) had received chemotherapy in the 6 months prior to hospitalization. 37 patients (8.1%) had thromboembolic events during their hospital stay. Age, race, receipt of chemotherapy, and history of hypertension, heart disease, obesity, and stroke were not predictive of thromboembolic events. Patients with thromboembolic events experienced significantly longer lengths of hospital stay than those without thromboembolic events (9 days vs 12 days, p<0.05).

Conclusion: Thromboembolic events affect many cancer patients with COVID-19 and may complicate their treatment course during hospitalization. Patients who experienced a thromboembolic event had prolonged hospital stays, which may lead to increased financial and emotional burden in this patient population. Evidence-based strategies for preventing thrombosis, including pharmacologic and mechanical methods, should be emphasized in hospitalized cancer patients with COVID-19, which may decrease thrombotic complications. Further, methods of secondary thrombosis prophylaxis, such as early detection with screening methods or treatment of subclinical methods, should be encouraged. Future studies should promote risk classification in this patient population and optimal prophylaxis paradigms.