**12.3 Time after diagnosis**

Several studies have demonstrated that the risk of VTE is highest in the initial time period following cancer diagnosis. In a population-based study of patients with thrombosis, the risk of developing VTE was highest in the first few months following the initial diagnosis of malignancy. A retrospective analysis of over 200 000 cancer patients from the California Cancer Registry revealed that the rate of VTE per patient-year in the first year after diagnosis of cancer was 3.3, compared with 0.8 in the second year after diagnosis 145. The rate of VTE in patients with colon cancer during the first 6 months after diagnosis is 5.0/100 patient-years, but this drops off dramatically to 1.4/100 patient-years in the next 6- month period 143.
