Smoking ups venous thromboembolism risk in cancer patients

Smoking increases the risk of venous thromboembolism (VTE) in cancer patients, but not in people without cancer, a recent study has found.

Drawing from the Scandinavian Thrombosis and Cancer cohort, the researchers looked at the interaction between cancer, smoking, and VTE in 105,382 individuals (mean age 51±14 years, 58,626 women). Cancer incidence was identified through linkage to the Danish Cancer Registry and the Cancer Registry of Norway. Cases of VTE were identified through a review of medical records.

During follow-up, 10,181 participants developed cancer. These individuals tended to be older (mean age, 58 vs 51 years) and were more likely to be smokers (55 percent vs 46 percent) as compared to the overall cohort.

Over a median duration of 11.6 years, 1,611 participants developed incident VTE, 214 of which were deemed related to active cancer. The resulting incidence rate of VTE was 1.4 per 1,000 person-years in the overall cohort and 14.1 per 1,000 person-years in the cancer subgroup. This corresponded to a more than eightfold increase in the risk of VTE in cancer patients (hazard ratio [HR], 8.27, 95 percent confidence interval [CI], 7.14–9.57).

Notably, the researchers also detected an interaction among VTE risk, cancer, and smoking. In particular, smoking increased the likelihood of VTE by nearly 50 percent in smokers (HR, 1.49, 95 percent CI, 1.12–1.98), but had no clear impact in nonsmokers (HR, 1.07, 95 percent CI, 0.96–1.20). Further adjustments for cancer site and metastasis had very little impact on the obtained risk estimates.