Genetic testing could help define VTE risk in patients with breast cancer
Genetic testing may help identify patients with breast cancer who have a high risk for venous thromboembolism, according to results of Swedish population-based study published in Clinical Cancer Research.
Genetic testing appeared more informative in older patients, results also showed.
“The risk for VTE is increased in [patients with cancer], particularly in those receiving chemotherapy,” Judith S. Brand, PhD, postdoctoral researcher in the department of medical epidemiology and biostatistics at Karolinska Institutet in Stockholm, Sweden, 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 a highly heritable and serious complication of cancer treatment. Although the incidence of VTE varies in patients with breast cancer, it appears to be highest shortly after diagnosis, during treatment with chemotherapy. Still, routine thromboprophylaxis is not recommended for patients undergoing chemotherapy.
Brand and colleagues examined the individual and joint effects of chemotherapy and genetic susceptibility of VTE risk in 4,261 Swedish women diagnosed with primary invasive breast cancer between 2001 and 2008.
Patients underwent risk stratification based on chemotherapy and their genetic susceptibility, derived from a polygenetic risk score (PRS) that included nine established VTE loci. A score in the top 5% indicated patients had a high genetic susceptibility for VTE.
During a median follow-up of 7.6 years, 276 patients experienced a VTE event.
Analyses adjusted for patient, tumor and treatment characteristics showed risk for VTE was greater in patients receiving chemotherapy (HR = 1.98; 95% CI, 1.40-2.80) and patients in the highest 5% of the PRS (HR = 1.90; 95% CI, 1.24-2.91). Patients with both characteristics had a 1-year cumulative incidence of 9.5%, whereas VTE incidence was 1.3% for patients without these risk factors (P < .0001).
Stratified analysis showed risk for VTE was greater among patients aged older than 60 years who had higher PRS scores (HR = 2.44; 95% CI, 1.37-4.35) than among younger patients (HR = 1.31; 95% CI, 0.67-2.55; P for interaction = .04).
One-year cumulative VTE incidence in older patients with both risk factors was 25%.
Brand and colleagues noted a limitation of the study was the small number of older patients who had chemotherapy and a high genetic susceptibility (n = 276 of 4,261), adding that larger-scale studies would be necessary to provide more risk estimates.
“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 high risk,” Brand said. “Because older patients demonstrated a stronger genetic effect and higher VTE incidence, this group requires special attention in future risk stratification efforts.” – by Chuck Gormley
Disclosure: The researchers report no relevant financial disclosures.