A large international clinical trial led by the National Cancer Center Singapore has found that taking aspirin for three years after standard therapy for high-risk colorectal cancer does not significantly reduce the risk of disease recurrence.
The findings, published in The Lancet Gastroenterology & Hepatology, offer important insights but underscore the complexity of finding effective post-treatment strategies for colorectal cancer.
Background on Colorectal Cancer and Aspirin’s Potential
Colorectal cancer ranks as the third most common cancer worldwide, with 2 million new cases and 1 million deaths in 2020. Despite advances in treatment, such as the addition of oxaliplatin to chemotherapy over 20 years ago, there has been little progress in significantly improving cure rates for high-risk patients.
Aspirin, a widely available and inexpensive drug, has drawn interest for its potential to improve cancer outcomes. As a COX-1 and COX-2 inhibitor, it has shown promise in reducing the risk of colorectal cancer and polyp recurrence in hereditary syndromes, supported by evidence from randomized trials.
However, its role as a post-treatment option for colorectal cancer patients has remained uncertain, prompting the ASCOLT trial to address this gap.
The ASCOLT Trial: Design and Methods
The ASCOLT trial, which began in 2009, was a phase 3, randomized, double-blind, placebo-controlled study designed to evaluate aspirin’s efficacy in preventing colorectal cancer recurrence.
The trial enrolled 1,587 participants from 66 centers across 11 countries, all of whom had completed surgery and at least three months of chemotherapy for Dukes’ C or high-risk Dukes’ B colorectal cancer.
Participants were randomly assigned to receive either 200 mg of aspirin daily or a placebo for three years. Over a follow-up period of five years, researchers monitored patients through regular clinical visits, imaging, and colonoscopies to assess disease recurrence and survival outcomes.
Key Findings
Disease-Free Survival (DFS):
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- Five-year DFS was 77.0% in the aspirin group compared to 74.8% in the placebo group.
- Hazard ratio (HR): 0.91; 95% confidence interval (CI): 0.73–1.13 (not statistically significant).
Overall Survival (OS):
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- Five-year OS was 91.4% in the aspirin group versus 88.9% in the placebo group.
- HR: 0.75; 95% CI: 0.53–1.07 (not statistically significant).
Subgroup Analysis:
A potential benefit was observed in patients who had not received oxaliplatin during chemotherapy, but this result was not statistically significant after correcting for multiple comparisons.
Safety:
Aspirin was well-tolerated, with no major safety concerns reported.
The ASCOLT trial showed that aspirin did not provide a statistically significant advantage in preventing colorectal cancer recurrence or improving survival in the overall patient population.
While the results leaned slightly in favor of aspirin, the confidence intervals crossed the threshold of no effect, meaning the observed differences could be due to chance.
These findings effectively rule out large benefits of aspirin as a secondary prevention strategy for colorectal cancer.
However, they do not exclude the possibility of modest effects, particularly in specific subsets of patients. For example, patients with certain genetic mutations, such as PIK3CA or COX-2 overexpression, may still derive benefit, as ongoing biomarker studies aim to clarify.
The ASCOLT trial represents a major step in understanding aspirin’s potential role in colorectal cancer care. While its findings do not support widespread use of aspirin for secondary prevention, they highlight the need for personalized approaches.
Ongoing biomarker research and a planned meta-analysis that combines data from similar trials may identify patient groups most likely to benefit from aspirin.
The ASCOLT trial demonstrates that while aspirin may not significantly prevent colorectal cancer recurrence in high-risk patients overall, its potential for modest benefits in specific subgroups remains an area for further investigation.
This research underscores the importance of tailoring post-treatment strategies and leveraging biomarkers to improve outcomes in colorectal cancer patients.
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The research findings can be found in The Lancet Gastroenterology & Hepatology.
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