VTE Risk Tied to Metastatic Disease in Breast Ca


SAN ANTONIO — The incidence of venous thromboembolism in the year following breast cancer diagnosis is roughly 1%, Dr. Helen K. Chew reported at a breast cancer symposium sponsored by the Cancer Therapy and Research Center.

That's a lower figure than previously reported in some clinical trials. But the trials typically feature lengthy exclusion criteria and involve hundreds of patients, whereas Dr. Chew's data carry the authority of big numbers: to be exact, all 108,255 women with breast cancer diagnosed in California during a 4-year period and followed through the California Cancer Registry and California Patient Discharge Data set.

By far the strongest predictor of venous thromboembolism (VTE) in this cohort was the presence of metastatic disease at breast cancer diagnosis. It was associated with a 6.3-fold increased risk, compared with patients who had localized cancer, said Dr. Chew, director of the breast cancer program at the University of California, Davis, cancer center.

The incidence of VTE was 0.6% in the first 6 months following breast cancer diagnosis and a cumulative 0.9% at the 12-month mark. It fell off thereafter such that the cumulative 2-year incidence was 1.2%.

In a multivariate analysis, regional disease at the time of breast cancer diagnosis—present in 31% of patients—was associated with a 2.2-fold increased risk of subsequent VTE, compared with localized disease, which was present in 61% of the women. Women age 65 or older had an 80% greater risk than those younger than 45.

The presence of a single comorbidity was associated with a 2.2-fold greater risk of VTE than in women with no comorbid conditions; patients with three comorbid conditions had a 3.3-fold increased risk, compared with those who had none.

Women of Asian heritage were 70% less likely to experience VTE than whites. Patients who underwent major surgery were half as likely to develop VTE as those who didn't, although Dr. Chew suspects the association isn't causal and more likely reflects localized disease and overall good health. “Patients with metastatic disease generally wouldn't undergo breast cancer surgery,” she noted.

Breast cancer histology wasn't predictive of VTE risk.

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