Aspirin lowers metastasis risk in bowel cancer patients with PIK3 mutation, study says

A Swedish-led randomized trial has found that daily aspirin after bowel cancer surgery reduced the risk of metastasis by 55% in patients with a mutation in the PIK3 signaling pathway, compared with a placebo over three years of follow-up. Published in The New England Journal of Medicine, the results point to aspirin as a potential, low-cost addition to treatment for a subset of colorectal cancer patients.

Researchers enrolled more than 3,500 patients from 33 hospitals across Sweden, Norway, Denmark and Finland. About 40% carried the PIK3 mutation. Participants were randomly assigned to receive 160 milligrams of aspirin daily or a placebo for three years following tumor-removal surgery. In the mutation-positive group, those taking aspirin had a 55% lower risk of metastasis than those on placebo.

Lead author Anna Martling, a professor at Karolinska Institutet, said aspirin is readily available globally and extremely inexpensive compared with many modern cancer drugs, which is very positive for patients and healthcare systems. She described the study as a new context for precision medicine and said it demonstrates how genetic information can guide treatment while potentially reducing suffering and costs."This is a clear example of how we can use genetic information to personalise treatment and at the same time save both resources and suffering," Martling added.

The trial follows years of observational work that hinted aspirin could influence cancer risk and recurrence, but this study is the first randomized trial to confirm the association in a defined genetic subgroup. Researchers say the effect likely stems from aspirin's anti-inflammatory action, which may create an internal environment less favorable to cancer cells while slowing tumor spread.

Bowel cancer, which includes colon and rectal cancers, is among the deadliest and most challenging cancers to treat when it recurs or metastasizes. Worldwide, about two million people are diagnosed with colorectal cancer each year, and 20% to 40% of cases develop metastases. In the United Kingdom, roughly 44,000 new bowel cancer cases are diagnosed annually, with about 130,000 cases in the United States. The disease is responsible for roughly 17,000 deaths per year in the UK and around 50,000 in the United States, and just over half of bowel cancer patients survive 10 years after diagnosis.

Aspirin is a long-standing medicine used to relieve pain and inflammation and, in low doses, to prevent blood clots. It can cause stomach irritation and other side effects, so people with stomach ulcers, bleeding disorders or asthma are advised to avoid it unless prescribed by a clinician.

Experts stressed that the findings specifically apply to patients with the PIK3 mutation and may not extend to all individuals with bowel cancer. If confirmed in broader populations, the results could influence post-surgical care and prompt genetic testing to identify those who might benefit from aspirin as part of a personalized treatment plan. Additional studies are expected to assess long-term outcomes, optimal dosing, and safety in diverse patient groups.