Could your daily aspirin prevent colorectal tumors? New research suggests the one-a-day habit could indeed prevent it from developing or spreading in some patients, with potential implications for future drugs. 

Researchers from the University Hospital of Padova in Italy described how they found that patients with colorectal cancer who took aspirin daily had greater expression of a protein associated with identifying and destroying immune cells. They replicated their results, which were detailed in a study published April 22 in the American Cancer Society’s journal Cancer, in cell lines. 

The results hint at the possibility that altering aspirin in ways that improve its absorption in the colon could make it more effective against colorectal cancer, study lead Marco Scarpa, M.D., Ph.D., said in a press release. 

“Our study shows a complementary mechanism of cancer prevention or therapy with aspirin besides its classical drug mechanism involving inhibition of inflammation,” he said.

Given that oral aspirin absorption varies throughout the colon, “if we want to take advantage of its effects against colorectal cancer, we should think of how to guarantee that aspirin reaches the colorectal tract in adequate doses to be effective,” he added. 

Decades of evidence in animals and humans suggests that non-steroidal anti-inflammatory drugs, or NSAIDS—including aspirin—can prevent or slow colorectal cancer prevention. Some studies in mice showed that the drug worked by reducing inflammation, while others pinned down mechanisms specifically related to anti-tumor gene expression. Randomized clinical trials have shown that aspirin reduces the risk of colorectal cancer recurrence and mortality as well as abnormal polyps. 

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For the new study, the researchers examined healthy and tumor samples from 238 patients with colorectal cancer who had their tumors removed between 2015 and 2019. Around 30 of them took aspirin daily; in these patients, immune cells in their colon tissue expressed higher levels of CD80, a protein involved in what’s known as tumor surveillance. Tumor surveillance, or immune surveillance, is the tracking and removal of cancerous cells by the immune system. 

The patients who took aspirin daily also had less cancer spread to the lymph nodes and greater amounts of immune cells in their tumors. The researchers validated their findings in colorectal cancer cell lines treated with aspirin, which caused them to express CD80. 

“These data suggested that regular aspirin use may have an active role in enhancing immunosurveillance against [colorectal cancer],” the researchers concluded in the paper’s abstract. 

There are some drawbacks to daily aspirin use, most crucially the risk of internal bleeding and strokes—concerns that in 2021 led the U.S. Preventive Services Task Force to make changes to its long-standing recommendation that adults who are at elevated risk of heart disease take the drug daily for its cardiac benefits. Pharma companies have been working on formulations that have better absorption with lower risks. One option is PLx Pharma's Vazalore, which curbs GI symptoms with a lower rate of ulcers and erosions than plain aspirin. 

Meanwhile, research on the potential for aspirin to prevent or treat colorectal cancer continues in clinical trials. One study at Massachusetts General Hospital is currently recruiting for people to take part in a 10-year study to see whether daily low-dose aspirin reduces the risk of cancer development, while another is currently underway that looks at whether the drug is helpful as an adjuvant to other types of treatments in patients whose tumors have certain genetic changes.