Aspirin Cuts Colon Cancer Recurrence by Half — In the Right Patients

Surgeons at Karolinska University Hospital in Stockholm have spent years watching colon cancer come back. They operate, they remove the tumor, they send patients home — and then, sometimes, the disease returns anyway. So when researchers there ran a clinical trial testing whether a cheap painkiller could change that story, expectations were modest. The results were not.

The Drug That's Been Under Your Nose All Along

Aspirin has been around since 1899. In Indian households, it's known by a dozen brand names, prescribed for heart attacks and fevers, available at any chemist for less than the price of a chai. Nobody thought of it as a cancer drug. That's precisely what makes the ALASCCA trial, published in the New England Journal of Medicine, so surprising.

The trial gave 3,500 colorectal cancer patients either 160 mg of aspirin daily or a placebo — for three full years after surgery. Simple setup. Enormous scope: 33 hospitals across Sweden, Norway, Denmark, and Finland. And the findings landed with enough force that the medical community is paying close attention.

Here's the catch though. Not every patient benefited. Not even close.

Colon Cancer After Surgery — The Problem That Persists

Colorectal cancer is the third most diagnosed cancer globally, with nearly two million new cases every year. In India, rates have been rising steadily, particularly among urban populations under 50 — a demographic shift that oncologists describe as worrying. Surgery remains the primary treatment for early-stage disease, but the problem is what happens next.

Even after a technically successful operation, cancer cells can linger. They spread through the bloodstream before anyone catches them. They settle elsewhere. They wait. That's why recurrence — the disease returning months or years after surgery — remains the central nightmare of colorectal cancer care. Existing adjuvant chemotherapy helps in some cases, but carries serious side effects and doesn't work for everyone. For decades, the options after surgery have been frustratingly limited.

That gap is what the Karolinska team was trying to close. And the path they chose was, to put it plainly, cheap.

Why Does Aspirin Work Against Cancer in Some Patients?

This is the question the researchers are still working through — and the honest answer is: not fully understood yet. What they do know is that aspirin attacks cancer through several overlapping mechanisms at once. It reduces chronic inflammation, which tumors exploit to grow. It interferes with platelets — the blood cells that can inadvertently shield circulating cancer cells from the immune system. And it appears to directly disrupt certain signaling pathways inside tumor cells, including the very PI3K pathway that's disrupted in mutation-carrying patients.

That last point matters. The researchers believe that when the PIK3CA pathway is already mutated, aspirin's interference hits harder — like jamming a lock that's already partially broken. The drug essentially compounds the dysfunction that the mutation has already introduced, making it harder for remaining cancer cells to survive and multiply after surgery.

What the Trial Numbers Actually Show

Among patients whose tumors carried PIK3CA mutations, cancer came back in 7.7% of those taking aspirin — versus 14.1% in the placebo group. A similar pattern held for patients with related PI3K pathway alterations: recurrence at 7.7% on aspirin, compared to 16.8% on placebo. In both cases, aspirin roughly halved the risk of the disease returning.

Disease-free survival also shifted meaningfully. Close to 89% of aspirin-treated patients in the target group remained cancer-free after three years, against roughly 79–81% in the placebo group. Those aren't marginal numbers. For a drug that costs almost nothing and requires no hospital visit to administer, the gap is striking.

But the trial also found something worth taking seriously: severe side effects showed up in 16.8% of aspirin patients, versus 11.6% in the placebo group. Aspirin isn't harmless at daily doses, particularly for people with stomach ulcers, bleeding disorders, or kidney issues. The benefit is real — and so is the risk profile.

What This Means for Patients — and What's Still Unknown

No oncologist is going to start prescribing aspirin to every colon cancer patient tomorrow. The findings need replication. The side effect data needs to be weighed carefully for individual patients. And genetic testing for PIK3CA mutations — while becoming more accessible — isn't yet standard in most Indian hospitals outside of major cancer centres.

What the ALASCCA trial does is shift the conversation. It turns aspirin from a folk remedy into a serious candidate for precision oncology. It demonstrates that a drug's effectiveness can depend entirely on the genetic makeup of the tumor, not just the tumor's location or stage. And it raises a pointed question for the medical community: how many other cheap, existing drugs might work similarly well — if only we knew which patients to give them to?

Anna Martling's team plans further analysis of long-term outcomes and a closer look at which specific mutation subtypes drive the strongest benefit. The results at the five-year mark, when they arrive, will be watched closely.

• Genetics unlocks the benefit — Aspirin only cuts recurrence risk in colorectal cancer patients with PIK3CA or related PI3K pathway mutations; without the mutation, there's no evidence of benefit.
• The drug is already here — Unlike most precision cancer therapies that cost lakhs per cycle, aspirin is globally available and costs almost nothing, which could make it accessible across income levels if guidelines adopt this approach.
• Side effects are real — Nearly 17% of patients on daily aspirin experienced severe adverse events, so this is not a self-prescribed solution — genetic testing and physician oversight would be essential before starting treatment.

"Aspirin is a drug that is readily available globally and extremely inexpensive compared to many modern cancer drugs, which is very positive." — Anna Martling, New England Journal of Medicine, 2025.