Impact of Venous Thromboembolism on Mortality of Elderly Medicare Patients with Stage III Colon Cancer

Abstract

The improvement in survival rates for patients with colon cancer has shifted the focus from examining cancer-specific mortality to exploring all-cause mortality. Adverse events such as venous thromboembolism (VTE) affect overall survival times and the net clinical benefit of cancer management strategies. This retrospective study used Surveillance, Epidemiology and End Results (SEER) Medicare data to examine VTE incidence and mortality rates for elderly patients with stage III colon cancer who were diagnosed in 2004 or 2005 and followed through 2007. The impact of VTE on mortality was estimated using multivariable Cox proportional hazards regression. In all, 20.7% of 4,985 elderly patients with stage III colon cancer had clinically diagnosed VTE following diagnosis. All-cause mortality risk was higher for patients with a VTE diagnosis (hazard ratio [HR]: 1.15, 95% confidence interval [CI]: 1.04-1.27), greater comorbidity burden, more advanced tumor depth and nodal involvement within stage III, advanced age, and male sex; the risk was lower for patients treated with chemotherapy. VTE was associated with higher mortality hazards (HR: 1.41, 95% CI: 1.21-1.64) for patients treated with adjuvant chemotherapy but not for untreated patients. A new diagnosis of VTE significantly reduced survival rates for elderly patients with stage III colon cancer and further reduced survival rates for patients treated with chemotherapy. Improved prevention and management of VTE for elderly patients with stage III colon cancer who are at risk for VTE is warranted, particularly for patients treated with chemotherapy.