Clinical trial finds no benefit from aspirin in preventing colorectal cancer recurrence

A new international clinical trial led by the National Cancer Center Singapore is reporting that three years of aspirin following standard adjuvant therapy for high-risk Dukes’ B and C colorectal cancer did not yield a significant advantage in preventing disease recurrence.

Colorectal cancer is the third most prevalent cancer worldwide, with 2 million new cases and 1 million deaths reported in 2020. Over two decades since oxaliplatin’s incorporation as an add-on to colorectal cancer therapy, no new additional treatments have significantly improved cure rates.

Aspirin is inexpensive, globally available, and often investigated as a possible way to improve patient outcomes. As a COX-1 and COX-2 inhibitor, it has shown potential for reducing polyp recurrence and colorectal cancer risk in hereditary syndromes, with evidence well supported by prior randomized trials.

Data on aspirin’s efficacy as a post-cancer treatment have remained inconclusive. The ASCOLT trial began in 2009 and was designed to provide robust, randomized evidence.

In the study, “Aspirin after completion of standard adjuvant therapy for colorectal cancer (ASCOLT): an international, multicentre, phase 3, randomized, double-blind, placebo-controlled trial,” published in The Lancet Gastroenterology & Hepatology, researchers present findings from the study.

ASCOLT enrolled 1,587 participants at 66 centers across 11 countries or territories. Investigators included adults with Dukes’ C or high-risk Dukes’ B colon cancer or Dukes’ B or C rectal cancer who completed resection and at least three months of chemotherapy.

Patients were randomly assigned in a 1:1 ratio to receive either aspirin 200 mg daily or a placebo for three years. Follow-up spanned five years, with regular clinical visits and recommended imaging and colonoscopies to identify disease recurrences.

Results demonstrated that the aspirin group had a five-year disease-free survival rate of 77.0% compared to 74.8% in the placebo group (HR: 0.91; 95% CI: 0.73–1.13). Similarly, the aspirin group had a five-year overall survival rate of 91.4% versus 88.9% in the placebo group (HR: 0.75; 95% CI: 0.53–1.07). Investigators reported no statistically significant difference in the prevention of colorectal cancer recurrence.

While the outcomes appeared favorable in both cases, the confidence intervals for the hazard ratios cross 1, which represents the point of no effect. This indicates that the positive trends are not statistically significant, leaving open the possibility that the actual impact might range from beneficial to negligible or even slightly harmful (though unlikely in the case of aspirin).

Subgroup analysis hinted at a potential benefit in patients not treated with oxaliplatin during adjuvant therapy, but after multiple comparison adjustments, this observation lacked statistical significance.

The ASCOLT trial provides the first randomized evidence of aspirin’s role in secondary colorectal cancer prevention. It effectively rules out large benefits but leaves open the possibility of modest effects, perhaps in specific subsets of patients.

Ongoing biomarker studies within ASCOLT are working to identify subsets of patients who may benefit from aspirin, such as those with PIK3CA mutations or COX-2 overexpression. A planned meta-analysis incorporating results from similar trials will further clarify aspirin‘s role.

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