There is uncertainty about risk heterogeneity for venous thromboembolism (VTE) in older patientswith advanced cancer and whether patients can be stratified according to VTE risk. We performeda retrospective cohort study of the linked Medicare-Surveillance, Epidemiology, and End Resultscancer registry in older patients with advanced cancer of lung, breast, colon, prostate, or pancreasdiagnosed between 1995–1999. We used survival analysis with demographics, comorbidities, andtumor characteristics/treatment as independent variables. Outcome was VTE diagnosed at leastone month after cancer diagnosis. VTE rate was highest in the first year (3.4%). Compared toprostate cancer (1.4 VTEs/100 person-years), there was marked variability in VTE risk (hazardratio (HR) for male-colon cancer 3.73 (95% CI 2.1–6.62), female-colon cancer HR 6.6 (3.83–11.38), up to female-pancreas cancer HR 21.57 (12.21–38.09). Stage IV cancer and chemotherapyresulted in higher risk (HRs 1.75 (1.44–2.12) and 1.31 (1.0–1.57), resp.). Stratifying the cohort bycancer type and stage using recursive partitioning analysis yielded five groups of VTE rates(nonlocalized prostate cancer 1.4 VTEs/100 person-years, to nonlocalized pancreatic cancer17.4 VTEs/100 patient-years). In a high-risk population with advanced cancer, substantialvariability in VTE risk exists, with notable differences according to cancer type and stage
