OBJECTIVES : Non-Hodgkin lymphoma (NHL) and its treatment are associated with an increased incidence of venous thromboembolism (VTE). Our goal was to determine the risk of VTE associated with chemo-immunotherapy and examine differences by race/ethnicity and histologic subtype.

METHODS : We conducted a nested case-control study from within a retrospective cohort of 29,102 patients greater than 66 years of age with a histologically confirmed first primary NHL using, the Surveillance, Epidemiology and End Results (SEER) Medicare linked database. VTE cases were identified from health claims data and matched to up to ten controls on age, sex, race/ethnicity, and NHL subtype, using incidence density sampling. We determined relative risk of treatment-related VTE using multivariable conditional logistic regression models to calculate adjusted OR and 95% CI.

RESULTS : Among 2,592 cases and 18,518 matched controls, the median age was 78 years and most patients were female (56%), non-Hispanic white (96%) and diagnosed with diffuse large B-cell lymhpoma (70%). Overall, any use of chemo-immunotherapy was associated with increased risk of VTE (OR 1.18, 95% CI 1.05, 1.33). The greatest risk was observed in patients receiving chemo-immunotherapy within the last 30 days (OR 2.80, 95% CI 1.56, 5.05) and this remained elevated through the first 90 days post-treatment. In stratified analyses, VTE risk did not appear to differ significantly by race/ethnicity, although increased VTE risk was most consistently observed in patients with indolent NHL subtypes (OR 2.04, 95% CI 1.62, 2.55).

CONCLUSIONS : The first 90 days following initiation of chemo-immunotherapy treatment presents the highest risk of VTE among any chemotherapy treatment for NHL. Thromboprophylaxis strategies in patients with NHL may be most critical during this period. Consideration should also be given to older patients with indolent forms of lymphoma when initiating aggressive systemic therapy versus observation only.