Higher Long-Term Risk of VTE in Breast Cancer Patients Confirmed

Venous thromboembolism (VTE) is significantly more likely over the long term in breast cancer patients than in the general population, according to a study in Sweden. A number of factors raise one’s risk, including cancer-specific factors such as larger tumor size, progesterone receptor status, and others.

“Although the absolute risk of VTE is relatively low for breast cancer patients in comparison with other cancer populations, the long-term consequences in terms of morbidity and quality of life are substantial,” wrote study authors led by Judith S. Brand, PhD, of Karolinska Institutet in Stockholm. Also, because breast cancer is among the world’s most common malignancies, related VTE cases contribute much to healthcare costs.

Few studies have examined the independent contributions of tumor, treatment, and other patient-related factors to the risk of VTE. The new study included 8,338 breast cancer patients in Sweden, and compared them with 39,013 age-matched reference individuals from the general population. The results were published online ahead of print in Cancer.

A total of 426 breast cancer patients experienced a VTE during a median follow-up period of 7.2 years. These patients were younger at the time of VTE diagnosis (62 years) than those in the general population (65.3 years). The breast cancer patients had a hazard ratio (HR) for VTE compared with the general population of 3.28 (95% CI, 2.87–3.74).

This relative risk was highest early on, in the first 6 months after breast cancer diagnosis (HR, 8.62 [95% CI, 6.56–11.33]), and remained high at 12 months (HR, 4.46 [95% CI, 3.52–5.66]). It remained largely constant at time points beyond that, with an HR at 2 years of 2.01 (95% CI, 1.50–2.70) and at 7 years of 2.26 (95% CI, 1.70–2.99).

A number of factors were significant predictors of VTE on a multivariate analysis. For example, tumor size > 40 mm yielded a 1.55-fold risk compared to tumors 10 mm or below in size (95% CI, 1.02–2.35). Progesterone receptor (PR)-negative patients had an HR of 1.33 (95% CI, 1.03–1.71) for VTE compared with PR-positive patients. Pre-existing VTE, older age, comorbid disease, receipt of chemotherapy and endocrine therapy, and having more than four affected lymph nodes also raised the VTE risk.

The authors noted that thromboprophylaxis can lead to a reduction in VTE incidence, but it is not generally recommended in breast cancer patients because of side effects and a low baseline risk. “Selected high-risk patients, however, could potentially benefit from prophylactic or early detection measures,” they wrote. Though there are some VTE risk prediction models available, they noted that further study is still needed to assess the added value of some laboratory parameters as well as the risk factors found in this study.