Aspirin use failed to reduce recurrence rates among women with breast cancer in a phase 3, randomized, controlled trial that was halted following a planned futility analysis. The aspirin group actually had greater risk of recurrence, though the result did not reach statistical significance. Aspirin has proven effective in reducing recurrence rates in colon cancer.
Despite the disappointment of the results, Wendy Chen, MD, of Dana-Farber Cancer Institute, Boston, emphasized the value of the study. “Negative studies provide important data. You don’t want people doing something that’s not going to be helping them. There have been a lot of negative studies that have still provided important clinical information,” said Chen, who presented the results of the study at the ASCO Plenary Series.
Even study participants took the news with equanimity. “What has really been gratifying is that the patients, when we did tell them about the results, all of them [said] ‘I’m really glad I participated in the study anyway. I think it was an important question.’ And this is why we do studies. You don’t do studies because every single one of them is going to show a benefit. We do studies knowing that some of them are going to show no benefit,” said Chen.
The study included 3,021 women under age 70, recruited from 338 sites between 2017 and 2020, who were randomized to 300 mg daily aspirin or placebo. The median follow-up was 24.0 months. Dropout was high, with only 56% of patients still taking aspirin or placebo at the end of the study. The percentage was nearly identical in both arms. That low treatment rate could potentially explain the lack of an apparent effect, but Chen noted that the incidence of recurrence was actually higher in the aspirin group (hazard ratio, 1.25), though the result was not statistically significant (P= .1258). “The amount that it would need to flip in the second half [of the study] would really be of such a large magnitude to flip it. That biologically would not be plausible,” Chen said.
Previous epidemiological and even post hoc analyses of other clinical trials had suggested that aspirin might be effective at reducing recurrence in breast cancer, including data from 39,876 participants in the Women’s Health Study suggesting a reduction in risk of metastatic adenocarcinoma, but this isn’t the first time such evidence has led researchers and physicians astray. Chen pointed to hormone replacement therapy, which was prescribed for the prevention of breast cancer recurrence on the basis of similar evidence, but was shown to be harmful in a randomized, controlled trial.
“It was a very similar situation. Fortunately, the aspirin in this population was not causing harm, but it is possible that there are a lot of people who are just taking aspirin on their own, and they may be over 70, or they may have have other risk factors for adverse events that are different from our population,” Chen said.
The study was funded by the U.S. Department of Defense and the National Cancer Institute. Bayer provided aspirin and placebo for the study.
This story originally appeared on MDedge.com, part of the Medscape Professional Network.
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