Doctors Surprised by the Power of a Simple Drug Against Colon Cancer

A common medication may be taking on an unexpected role in cancer care.

What if a cheap, everyday painkiller could help keep cancer from coming back after surgery? New clinical trial results suggest that for some patients with colorectal cancer, aspirin may do exactly that.

In a study led by researchers at Karolinska Institutet and Karolinska University Hospital in Sweden, patients with colorectal cancer who took a daily low dose of aspirin after surgery were far less likely to see their disease return, but only if their tumors carried specific genetic changes.

The study zeroed in on alterations in the PI3K signaling pathway, which helps control how cells grow and survive. When this pathway is disrupted by mutations, it can drive cancer development. About 37 percent of patients in the trial had these genetic changes, making them eligible for targeted analysis.

Trial Results and Recurrence Risk

Participants were randomly assigned to take either 160 mg of aspirin each day or a placebo for three years following surgery. The results showed a clear benefit. Among patients with key PIK3CA mutations, cancer returned in 7.7 percent of those taking aspirin, compared to 14.1 percent in the placebo group. Patients with related genetic alterations saw similar results, with recurrence rates of 7.7 percent versus 16.8 percent. Overall, aspirin cut the risk of recurrence by roughly half.

The trial, known as ALASCCA, included more than 3,500 patients treated at 33 hospitals across Sweden, Norway, Denmark, and Finland. It is one of the first randomized studies to confirm earlier hints from observational research that aspirin might improve outcomes after a colorectal cancer diagnosis.

Colorectal cancer remains a major global health challenge, with nearly two million new cases diagnosed each year. Even after surgery, many patients face a significant risk that the disease will return, particularly if cancer cells have already spread beyond the original tumor.

“Aspirin is being tested here in a completely new context as a precision medicine treatment. This is a clear example of how we can use genetic information to personalize treatment and at the same time save both resources and suffering,” says first author Anna Martling, professor at the Department of Molecular Medicine and Surgery, Karolinska Institutet, and senior consultant surgeon at Karolinska University Hospital.

How Aspirin May Work

Researchers believe aspirin works through several overlapping mechanisms. It can reduce inflammation, limit platelet activity that may help cancer spread, and interfere with tumor growth. Together, these effects may make it harder for remaining cancer cells to take hold after surgery.

“Although we do not yet fully understand all the molecular links, the findings strongly support the biological rationale and suggest that the treatment may be particularly effective in genetically defined subgroups of patients,” says Anna Martling.

The study also pointed to improved disease-free survival, with close to 89 percent of aspirin-treated patients remaining cancer-free after three years, compared to roughly 79 to 81 percent in the placebo group. However, the treatment was not without risks. Severe side effects were reported in 16.8 percent of patients taking aspirin, versus 11.6 percent of those receiving a placebo.

Benefits, Risks, and Accessibility

What makes the findings especially notable is the accessibility of the treatment. Aspirin is already widely available around the world and costs far less than most modern cancer therapies. If future guidelines adopt this approach, genetic testing could help identify which patients are most likely to benefit from adding aspirin to their treatment plan.

“Aspirin is a drug that is readily available globally and extremely inexpensive compared to many modern cancer drugs, which is very positive,” says Anna Martling.

Reference: “Low-Dose Aspirin for PI3K-Altered Localized Colorectal Cancer” by Anna Martling, Ida Hed Myrberg, Mef Nilbert, Henrik Grönberg, Fredrik Granath, Martin Eklund, Tom Öresland, Lene H. Iversen, Carola Haapamäki, Martin Janson, Karin Westberg, Josefin Segelman, Urban Ersson, Mattias Prytz, Eva Angenete, Rebecka Bergström, Markus Mayrhofer, Bengt Glimelius and Johan Lindberg, 17 September 2025, New England Journal of Medicine.
DOI: 10.1056/NEJMoa2504650

The study was funded in part by the Swedish Research Council and the Swedish Cancer Society. The researchers state that there are no conflicts of interest.

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