Impact of time since diagnosis and mortality rate on cancer-associated venous thromboembolism: the Scandinavian Thrombosis and Cancer (STAC) cohort

Essentials Competing risk by death may lead to overestimation of venous thromboembolism (VTE) risk in cancers. We assessed the risk of VTE in cancer with and without accounting for competing risk by death. The risk of VTE was influenced by the mortality rate and the time since cancer diagnosis. Competing risk by death should be taken into account when exploring VTE risk in cancer.

SUMMARY

Background Venous thromboembolism (VTE) is a common complication in cancer, and studies have suggested that aggressive cancers create the highest risk of VTE. However, competing risk by death may result in overestimation of VTE risk in patients with cancers associated with high mortality. Therefore, we estimated the risk of VTE by cancer site, accounting for the differential mortality between cancers. Methods The Scandinavian Thrombosis and Cancer cohort included 144 952 participants followed from 1993-1997 to 2008-2012. Incidence rates, cause-specific hazard ratios (HRs) and subdistribution HRs (SHRs) were assessed for overall cancer and by cancer site according to time intervals since cancer diagnosis. Results During follow-up, 14 272 subjects developed cancer, and 567 had cancer-related VTE. In cause-specific analyses, the VTE risk was highest in the first 6 months after cancer diagnosis (HR 17.5, 95% confidence interval [CI] 15.1-20.3), and declined rapidly thereafter. However, when mortality was taken into account, the risk was similar in the periods 6 months before (SHR 4.8, 95% CI 3.6-6.4) and 6 months after (SHR 4.6, 95% CI 3.9-5.4) cancer diagnosis. The range of the 2-year cumulative VTE incidence rates was substantially narrowed for all cancer sites after competing risk by death was taken into account (from 1-10% to 1-4%). Conclusion VTE risk by cancer site was influenced by the mortality rate and the time since cancer diagnosis. Our findings suggest that the cancer itself is a major contributor to VTE risk, and that competing risk by death should be taken into account when VTE risk in cancer is explored.

The impact of initial cancer stage on the incidence of venous thromboembolism: the Scandinavian Thrombosis and Cancer (STAC) Cohort

Essentials Impact of cancer stage on venous thromboembolism (VTE) risk is not well-known in all cancers. The Scandinavian Thrombosis and Cancer Cohort provides person-time data and validated VTEs. Impact of cancer stage on VTE incidence tended to vary with cancer type. Cancer stage may not per se be a risk factor for VTE in all cancer types.

SUMMARY

Background Absolute measures of the impact of cancer stage on the incidence of venous thromboembolism (VTE) in patients with distinct cancer types have not been investigated in a large population-based cohort study. Objectives To investigate differences in the incidence rates of objectively confirmed VTE according to the development of cancer in a large population-based cohort study. Cancer type and stage at the time of diagnosis were taken into account. Patients and Methods The Scandinavian Thrombosis and Cancer Cohort includes data regarding cancer types, stages and objectively confirmed VTE diagnoses among 144 952 participants followed from 1993 to 2012. We studied stage-specific incidence rates of VTE, and calculated incidence rate differences (IRDs) for VTE according to stages in patients with 10 types of solid cancer. Results During the entire follow-up, 335 VTEs occurred, of which 293 occurred within 5 years. The IRD of VTE in patients with distant metastasis as compared with those with localized disease indicated large variation depending on cancer type. The highest IRD was observed for pancreatic cancer (IRD of 187.0 × 10-3 person-years [p-y]; 95% confidence interval [CI] - 6.7 to 380.8), and the lowest IRD was observed for prostate cancer (IRD of 3.7 × 10-3 p-y; 95% CI - 7 to 15.2). Regional spread as compared with localized disease also indicated large variation depending on cancer type; the highest IRD was observed for uterine cancer (IRD of 37.6 × 10-3 p-y; 95% CI - 23.7 to 99), and the IRDs for breast and prostate cancer were close to zero. Conclusion More advanced cancer at the time of diagnosis was associated with a higher risk of VTE, but the strength of the associations differed substantially between cancer types.