Aspirin fails to lower the risk of cancer recurrence when administered after curative-intent treatment for colorectal cancer liver metastases, according to final phase 3 trial results published in The Lancet Gastroenterology & Hepatology. The Scandinavian ASAC trial tracked 428 patients across 14 hospitals in Norway, Sweden, and Denmark to test whether the inexpensive, widely available drug could prevent the return of metastatic disease.
Aspirin Fails to Reduce Cancer Recurrence or Death in Trial
Led by Oslo University Hospital, the investigator-initiated trial randomly assigned 466 patients to receive either 160 mg of aspirin daily or a placebo following surgical resection or ablation of liver metastases. Among the 428 patients included in the primary analysis, aspirin did not reduce the risk of cancer recurrence or death compared to the control group, registering a hazard ratio of 1.08 with a 95.44% confidence interval spanning 0.85 to 1.38. Median disease-free survival stood at 1.13 years for patients taking aspirin, compared to 1.40 years for those receiving the placebo.
Researchers also evaluated whether specific genetic mutations altered the drug’s efficacy. Analysis revealed no evidence that aspirin’s effect differed across molecular subgroups defined by mutation status in the PIK3CA and KRAS genes. Professor Sheraz Yaqub of Oslo University Hospital and the University of Oslo, who led the trial, noted that the findings demonstrate why treatments must undergo rigorous randomised testing before doctors adopt them for new patient populations.
Contrasting Findings Between Metastatic and Non-Metastatic Disease
The ASAC results highlight a distinct clinical boundary regarding aspirin as an adjuvant treatment. Professor Per Sandström of Linköping University Hospital, the national principal investigator for the ASAC trial in Sweden, stated that with no demonstrated benefit and a higher rate of serious adverse events, routine initiation of aspirin solely to prevent recurrence in these patients lacks rationale.
Serious adverse events occurred in 7.8% of patients in the aspirin group, affecting 17 of 217 individuals, compared to 1.9% in the placebo group, where 4 of 211 patients experienced severe complications. No deaths were attributed directly to the study treatment. Three years after starting the treatment, overall survival reached 75.7% in the aspirin group and 84.9% in the placebo group, yielding a hazard ratio for death of 1.64. However, researchers cautioned that the trial was not originally powered to assess overall survival as a primary endpoint, and protocol data did not track treatments administered after initial recurrence.
Distinction Between New Initiation and Ongoing Prescribed Use
Clinical investigators emphasize that the ASAC trial specifically tested the effect of starting aspirin after treatment of liver metastases in patients who were not previously taking the drug. The study did not evaluate individuals who were already consuming aspirin for other medical indications before their cancer diagnosis. Yaqub advised that patients with preexisting medical prescriptions for aspirin should continue their regimen and consult their physician before making any changes.
The primary findings were presented as a Late-Breaking oral presentation at the American Society of Clinical Oncology Annual Meeting in Chicago before publication of the final analyses.
Frequently Asked Questions About the ASAC Trial
Who funded the ASAC trial?
The study received financial backing from the Research Council of Norway, the Norwegian Cancer Society, the Norwegian national programme for clinical treatment research (KLINBEFORSK), and Oslo University Hospital Fondsstiftelsen.
How many medical centres participated in the study?
The randomised, double-blind, placebo-controlled phase 3 trial was conducted across 14 hospital sites located in Norway, Sweden, and Denmark, coordinated by Oslo University Hospital.
What specific daily dose of aspirin did patients receive?
Patients assigned to the active treatment arm were given 160 mg of aspirin once daily following their curative-intent surgery or ablation.
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