Chemotherapy is known to carry a risk of venous thromboembolism in cancer patients, a particularly common risk in frequent cancers like breast cancer. But a genetic test may predict which of these patients are most likely to develop such serious blood clots, researchers report.
The study, “Chemotherapy, Genetic Susceptibility, and Risk of Venous Thromboembolism in Breast Cancer Patients,” published in Clinical Cancer Research, may help to identify patients most likely to benefit from prophylaxis treatment to prevent venous thromboembolism (VTE).
“The risk for venous thromboembolism [blood clots that form in a vein] is increased in cancer patients, particularly in those receiving chemotherapy,” Judith S. Brand, PhD, a postdoctoral researcher in the Department of Medical Epidemiology and Biostatistics at Karolinska Institutet in Stockholm, said in a press release. “As one of the most common cancers, breast cancer accounts for a large number of cancer-associated VTE cases.”
VTE is preventable through prophylaxis treatment with heparin, an anticoagulant. But because a side effect is less controllable bleeding, the drug is not routinely recommended to patients undergoing chemotherapy.
Researchers examined 4,261 Swedish women diagnosed with primary invasive breast cancer between 2001 and 2008. Risk stratification was based on chemotherapy use and genetic susceptibility, which was determined by a risk score assessing nine genes involved in VTE. Patients ranked in the highest 5 percent were classified as having a high genetic susceptibility.
Patients were followed for a median of 7.6 years, and 276 experienced a VTE during that time.
Results revealed that patients receiving either chemotherapy or with high genetic susceptibility were nearly twice as likely to experience a VTE event than those not using chemotherapy or with a low genetic susceptibility.
Patients carrying both risk factors also had a 9.5 percent one-year cumulative incidence of VTE, compared to only 1.3 percent in the lower-risk patient group.
Importantly, the risk associated with high genetic susceptibility was greatest among older patients. Indeed, patients age 60 or older who received chemotherapy and had high genetic susceptibility had a 25 percent one-year cumulative incidence of VTE.
“Breast cancer patients receiving chemotherapy are not routinely being examined for VTE prevention in today’s clinical practice. Our study demonstrates that information on genetic susceptibility can be used to identify patients at high risk of developing VTE,” Brand said.
“Combined with other clinical risk factors and biomarkers, these findings will guide future studies evaluating routine VTE risk assessment in chemotherapy outpatients, and prophylaxis for those at highest risk. Because older patients demonstrated a stronger genetic effect and higher VTE incidence, this group requires special attention in future risk stratification efforts,” she added.
The study had limitations, Brand also said, particularly the small number of older patients with genetic susceptibility who underwent chemotherapy, and noted that further research is needed to confirm these findings. In addition, researchers need to better understand the safety and potential benefit of giving anticoagulants to patients at high risk of VTE.