If you or someone you love has faced colorectal cancer surgery, a familiar pill might help keep the disease from coming back. A large Scandinavian clinical trial reports that a daily low dose of aspirin after tumor removal markedly decreases the chance of recurrence for a common genetic subset of colorectal cancers. Among patients whose tumors carry mutations in the PI3K signaling pathway, three-year recurrence rates were cut by roughly half compared with placebo. The findings, published in the New England Journal of Medicine, point to a simple, widely available option that could be added to post-surgical care for eligible patients. Experts say the results are strong enough to prompt serious discussions about routine genetic testing to guide aspirin use after surgery.
Who benefits most from aspirin after surgery
The benefit was concentrated in tumors with mutations in the PI3K pathway, a key driver of colorectal cancer biology. In the trial, genotyping identified these mutations in 1,103 patients out of 2,980 tested, or about 37 percent. That aligns with broader estimates that roughly 40 percent of colorectal cancers may harbor alterations in this pathway. For this subgroup, a daily aspirin regimen delivered a 55 percent lower likelihood of recurrence over three years compared with placebo. While not everyone stands to gain, the size of the eligible group means a substantial number of patients could be candidates for an affordable intervention.
What the ALASCCA trial tested
Called ALASCCA, the study was led by Prof Anna Martling at the Karolinska Institute and recruited across Sweden, Norway, Denmark, and Finland. More than 3,500 post-surgical colorectal cancer patients entered the study, and tumor genotyping was completed for 2,980 of them. Those with PI3K-pathway mutations were randomly assigned to receive either 160 mg of aspirin daily or a placebo for three years after surgery. The main outcome was whether the cancer returned during the follow-up period. Compared with placebo, aspirin recipients experienced a dramatically lower rate of recurrence, a result that could influence standard care in appropriately selected patients.
Why aspirin might work against recurrence
Aspirin’s anti-inflammatory action can temper the tumor-promoting inflammation that often surrounds residual cancer cells after treatment. Laboratory research also suggests aspirin may modulate PI3K signaling, which could impair growth and survival in cancers driven by this pathway. Another potential mechanism involves platelets, which can cloak circulating tumor cells, help them evade immune defenses, and seed metastases. By inhibiting platelet function, aspirin may make it harder for stray cancer cells to take hold. These intertwined effects offer a plausible explanation for the targeted benefit seen in PI3K-mutant tumors.
Colorectal cancer’s growing public health burden
Colorectal cancer affects nearly 2 million people worldwide each year, with tens of thousands of cases annually in the UK alone. Surgical advances, chemotherapy, and radiotherapy have improved outcomes, yet relapse remains a major challenge because microscopic cells can persist after treatment. Incidence is rising among people under 50, with lifestyle and metabolic factors, and even bacterial toxins in the gut, under investigation as contributors. Against this backdrop, a low-cost adjuvant such as aspirin, guided by tumor genetics, is an appealing way to close the recurrence gap. The ALASCCA results add to a growing push for more personalized prevention strategies after surgery.
Safety matters: balancing benefits and bleeding risk
Long-term aspirin is not risk-free. In the trial, four participants experienced serious adverse events that could be linked to aspirin, including allergic reaction, gastrointestinal bleeding, and intracranial hemorrhage. Four deaths occurred across both study arms, and one may have been aspirin-related. These events were uncommon, but they underscore the need to weigh bleeding risk carefully, especially in older adults or those with a history of ulcers, hemorrhagic stroke, or blood-thinning medication. Any consideration of aspirin after colorectal surgery should happen with a clinician who can tailor the decision to personal risk factors and preferences.
How this could change care
One clear implication is the value of routine tumor genotyping to identify patients with PI3K-pathway mutations who might benefit from post-surgical low-dose aspirin. Because aspirin is inexpensive and accessible, implementation could be swift if guided by genetics and embedded within standard follow-up care. Decisions should remain individualized, factoring in bleeding risk, comorbidities, and the need to continue proven treatments such as chemotherapy when indicated. Prior evidence supports this tailored approach, including trial data showing aspirin’s preventive effect in people with Lynch syndrome. With corroborating signals from studies funded by Cancer Research UK and others, guideline committees are likely to review the new data closely.
What we still need to learn
Key questions remain before aspirin becomes a universal recommendation after colorectal cancer surgery. Researchers need to confirm these results in broader and more diverse populations, and across different disease stages and tumor subtypes. Optimal dosing and duration are not fully settled, including whether benefits persist beyond the three-year window studied. Strategies to reduce bleeding risk, from better patient selection to structured monitoring, will be central to safe adoption. Finally, health-economic analyses and integration with other adjuvant therapies will help determine how aspirin fits into modern colorectal cancer care.
