Hopes that cheap, widely available aspirin could keep colorectal cancer from returning after liver surgery have been dealt a setback. The ASAC trial, a multicentre, phase 3, randomised, double-blind, placebo-controlled study run at 14 hospitals in Norway, Sweden and Denmark, with Karolinska University Hospital among the sites and Karolinska Institutet researchers involved, reported its final results in The Lancet Gastroenterology and Hepatology.
Patients who had undergone curative-intent treatment for liver metastases from colorectal cancer were randomised to 160 milligrams of aspirin daily or placebo for up to three years or until recurrence. Daily aspirin did not reduce the risk of recurrence or death, and serious adverse events were more common in the aspirin group than with placebo, an unfavourable balance for a preventive strategy in this setting.
The trial also probed a hypothesis raised by the earlier ALASCCA study in primary colorectal cancer, which had suggested benefit for patients with mutations in the PI3K signalling pathway. In ASAC, patients with such mutations did not benefit from aspirin after liver metastasis surgery. The investigators note the findings apply to starting aspirin after curative-intent treatment in people not already taking it, a precise but clinically important boundary for guidelines.