A review conducted by the US Food and Drug Administration (FDA) indicates that long-term use of the antiplatelet drug clopidogrel (Plavix) does not increase or decrease the overall risk of death in patients with, or at risk for, heart disease.
In addition, the FDA said there is no evidence to suggest that clopidogrel increases the risk of cancer or death from cancer.
These findings contradict those of the Dual Antiplatelet Therapy (DAPT) trial, the study that prompted the FDA’s review.
In this trial, researchers compared 12 months of DAPT (either clopidogrel or prasugrel plus aspirin) to 30 months of DAPT in patients who had a drug-eluting coronary stent.
Compared to patients taking clopidogrel for 12 months, patients who received clopidogrel for 30 months had lower rates of heart attacks and stent thrombosis but higher rates of death, primarily from cancer or trauma.
To investigate these findings, the FDA examined data from the DAPT trial and performed trial-level meta-analyses of other large, long-term trials.
The trials had a clopidogrel-plus-aspirin arm (long-term treatment was 12 months or longer) and a comparator arm of either aspirin alone or short-term clopidogrel plus aspirin (6 months or less). They also had a planned follow-up of at least 1 year.
All-cause death
In the DAPT trial, extended use of clopidogrel plus aspirin was associated with a significantly increased risk of death (2.2% for 30 months vs 1.5% for 12 months). But there was no increased risk for prasugrel plus aspirin (1.6% for 30 months vs 1.6% for 12 months).
The FDA’s initial meta-analysis on mortality included 12 trials (56,799 patients). The incidence of all-cause mortality was 6.7% for the long-term clopidogrel-plus-aspirin arm and 6.6% for the comparator arm, resulting in a Mantel Haenszel Risk Difference (MH RD) of 0.04% (95% CI, -0.35%-0.44%).
The FDA also conducted a meta-analysis of 9 of the 12 trials (45,374 patients), which enrolled patients with coronary artery disease or patients at risk of coronary artery disease. This analysis showed no difference in the risk of all-cause mortality—MH RD of -0.07% (95% CI, -0.43%-0.29%).
Cancer and death in DAPT
In the DAPT trial, the risk of cancer reported as an adverse event was not different between the 30-month (2.4% ) and 12-month (2.3%) groups receiving clopidogrel, when considering cancers reported after enrollment (from month 0 to 33 of the study).
The FDA performed several analyses of the cancer adverse event data, and the relative risk of cancer for the 30-month vs 12-month arm in the clopidogrel group ranged from 0.95 to 1.2, depending on the analysis.
Similar analyses for the prasugrel group revealed relative risks of cancer-related adverse events ranging from 1.4 to 1.6.
The FDA noted that, although there was no increase in the risk of cancer-related adverse events for clopidogrel in the 30-month arm, the risk of cancer-related death was higher than in the 12-month arm—0.7% and 0.2%, respectively.
For prasugrel, there was a trend toward a higher risk of cancer adverse events in the 30-month arm than in the 12-month arm, but the risk of cancer death was identical in both arms—0.4% vs 0.4%.
The FDA said these findings are difficult to reconcile.
Meta-analyses of cancer and death
The FDA performed 2 trial-level meta-analyses to investigate the role of clopidogrel in cancer and cancer death.
The first was an analysis of cancer-related adverse events from 4 trials (37,835 patients) that compared long-term clopidogrel and aspirin to either aspirin alone or short-term clopidogrel plus aspirin.
The incidence of cancer adverse events was 4.2% for the long-term clopidogrel-plus-aspirin arm and 4.0% for the comparator arm (MH RD of 0.19%; 95% CI, -0.2%-0.59%).
The FDA conducted the second meta-analysis to assess cancer-related death. The analysis included 5 trials (40,855 patients).
The incidence of cancer death was 0.9% for the long-term clopidogrel-plus-aspirin arm and 1.1% for the comparator arm (MH RD of -0.14%; 95% CI, -0.33%-0.06%).
The FDA said that, taken together, the results of this review do not suggest an increased risk of cancer adverse events, cancer-related death, or all-cause mortality with long-term clopidogrel therapy.
More details can be found in the FDA’s Drug Safety Communication on this topic.
