medwireNews: Long-term use of adjuvant endocrine therapy by women with a history of nonmetastatic breast cancer can significantly alter their risk for some types of cardiovascular disease, a meta-analysis shows.
The study by Anthony Matthews, from the London School of Hygiene and Tropical Medicine in the UK, and colleagues showed that the risk for venous thromboembolism (VTE) may be up to 7.1 times higher in tamoxifen users compared with nonusers in both randomized controlled trials (RCTs) and observational studies.
In line with this, the risk for VTE was up to 75% lower with aromatase inhibitors than with tamoxifen.
However, the direct effect of aromatase inhibitors on VTE was unclear, as only one RCT addressed this, finding a 1.8-fold increased risk for VTE in aromatase inhibitor users compared with placebo.
Nonetheless, Matthews et al say that these findings highlight “the need for clinical vigilance and possible preventive measures when prescribing endocrine therapies to women at risk of venous thromboembolism.”
The systematic review and meta-analysis included 15 randomized controlled trials and 11 observational studies that gave results for seven specific cardiovascular disease outcomes, namely VTE (n=15 studies), myocardial infarction (MI; n=14), stroke (n=12), angina (n=4), heart failure (n=4), arrhythmia (n=1), and peripheral vascular disease (n=1).
Compared with tamoxifen users, those given aromatase inhibitors had a 1.5–2.3-fold increased risk for MI and a 1.4-fold increased risk for angina, but the researchers suggest that these findings “may be partly driven by a protective effect of tamoxifen” on both MI and angina.
Indeed, the relative risks for MI and angina associated with tamoxifen use ranged from 0.2–1.2 and 0.4–0.9, respectively, versus no use.
However, Matthews and co-authors caution that most RCTs were underpowered to detect significant differences in VTE, MI, and angina, with only three finding clear evidence despite several others being suggestive of associations in the same direction.
Furthermore, there were limited and inconsistent data for all other cardiovascular endpoints.
Writing in The BMJ, the investigators say that the addition of observational studies to RCT has progressed knowledge on the impact endocrine therapies have on cardiovascular disease risk.
“However, further high quality evidence is still needed for several cardiovascular disease outcomes,” they add.
Matthews and team conclude: “Although the choice of aromatase inhibitor or tamoxifen will primarily be based on the effectiveness against the recurrence of breast cancer, this review shows that the individual patient’s risk of venous or arterial vascular disease should be an important secondary consideration.”
By Laura Cowen
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