Aspirin vs. Cancer: What Are We Waiting For?

I wrote that headline more than a decade ago, but the question remains the same! Why hasn’t the medical community recognized the anticancer action of aspirin? Aspirin remains one of the most inexpensive drugs in the pharmacy. A familiar brand name tablet costs less than 6 cents a pill. A bottle containing 300 tablets will set you back under $17. Despite the low price, the value of aspirin vs. cancer might be priceless.

A VERY Short History of Aspirin:

Native healers have been using the salicylates found in willow bark for thousands of years. Hippocrates, often described as the father of modern medicine, wrote about a powder from willow to control a fever and relieve pain.

A chemist for the Bayer Company synthesized aspirin in 1897. Perhaps because it is so old, so familiar and so inexpensive, it rarely gets the respect it deserves.

Aspirin vs. Cancer: The Story Goes Way Back!

We wrote about the anticancer benefits of aspirin in a book called The ASPIRIN Handbook: A User’s Guide to the Breakthrough Drug of the ’90s (Bantam Book, 1993). In it we had a chapter titled “Using Aspirin to Help Prevent Colon Cancer.”

Here is how we answered a question from a reader over 30 years ago:

“Q. Colon cancer runs in my family, so I would appreciate a complete explanation of what we know about how aspirin can help prevent it and all the physiology involved.”

“A. The story of aspirin against cancer got its start back in the early 1980s. Rats and other animals treated with carcinogens often develop tumors of the colon. This is thought to be a good model for human colon cancer, since the tumors are biologically similar. When the animals were also treated with NSAIDs (non-steroidal anti-inflammatory drugs) like aspirin, Indocin, (indomethacin),  Feldene (piroxicam), and Clinoril (sulindac), there was “inhibition of the growth of colon tumors.”

“This  fascinating discovery led to several small clinical studies in humans. Investigators found that people who are genetically predisposed to develop polyps (and are therefore at greater risk of colorectal cancer) could make the precancerous growths “regress” when they took Clinoril.

“The stage was set for epidemiological studies. Researchers analyzed drug use from several large databases. The investigators found that regular use of NSAIDs (including aspirin) appeared to roughly halve the incidence of colorectal cancer. It may also improve survival if cancer occurs.

“One current hypothesis is that by knocking out prostaglandins, aspirin, and other NSAIDs, may suppress cell growth necessary for tumor formation. These drugs may also indirectly stimulate the immune system.”

Fast Forward to 2025: Aspirin vs. Cancer of the Colon & Rectum:

A Swedish research study published in the New England Journal of Medicine (Sept. 18, 2025) concludes that aspirin can dramatically reduce the likelihood of colo-rectal cancer recurrence in selected patients.

This was a gold-standard randomized controlled trial. Patients who had their tumors removed received either 160 mg of aspirin (half a standard tablet) or placebo. They were followed for three years. These cancer patients had a common gene mutation called PIK3CA. There was a 7.7 percent recurrence rate in the aspirin takers compared to a 14 percent return in the people on placebo. That is a relative risk reduction of 50 percent.

This is hardly the first time we have heard that aspirin can be helpful against colorectal cancer. A study also published in the New England Journal of Medicine 34 years ago concluded:

“Regular aspirin use at low doses may reduce the risk of fatal colon cancer.” 

A systematic review published in the journal Public Health (Aug. 25, 2025) concluded:

“This meta-analysis of over 260 studies involving more than 78 million individuals found a consistent association between regular aspirin use and a lower risk of cancer incidence and mortality. Specifically, a 19% relative reduction was observed in both cancer-specific mortality and incidence. The effect was most pronounced in gastrointestinal (GI) malignancies—particularly colorectal, liver, and upper GI tract cancers.”

Other Research Documenting Aspirin vs. Cancer:

Aspirin has been shown to reduce the risk of one of the deadliest cancers–melanoma–a skin cancer that is notoriously hard to treat. The data came from the Women’s Health Initiative (WHI), one of the most important research initiatives in memory. You may recall that it was the WHI that uncovered risks of hormone replacement therapy (HRT). The study started in 1991 and followed over 160,000 postmenopausal women for at least 15 years.

Scientists continued to track many of the women who were recruited into the WHI. This study focused on the likelihood of developing melanoma in nearly 60,000 Caucasian women who participated in this program. They were tracked for 12 years. Those who took a standard aspirin tablet at least twice a week reduced their risk of developing melanoma by 21 percent. Women who regularly relied on aspirin for at least five years decreased their likelihood of being diagnosed with melanoma by 30 percent.

The lead investigator of the study, Dr. Jean Tang at Stanford University School of Medicine, told NPR, that

“In terms of cancer prevention, a lower melanoma risk by 20 percent is very large and significant… There’s nothing else that I know of that has as large an effect as what we’re seeing with aspirin.”

The Naysayers Don’t Like Aspirin vs. Cancer:

Despite this long-term study’s positive results there are a lot of naysayers when it comes to aspirin vs. cancer. Some point out that this was not a randomized, double-blind, placebo-controlled trial. It was “only” an observational study, meaning that the investigators compared self-reported aspirin users with women who said that they used NSAID (ibuprofen or naproxen) pain relievers or acetaminophen.

The gold standard would have been a study in which women were randomized to take aspirin, placebo, NSAIDs or acetaminophen. They would have been tracked for years to see whether there was a difference in outcome.

The only problem is that such a study will never be conducted because it would cost too much and our government is not likely to come up with the hundreds of millions such a study would require. No drug company would sponsor such a study since aspirin is dirt cheap and available generically.

Other Studies of Aspirin vs. Cancer:

If this were the only study suggesting that aspirin might be beneficial in preventing hard-to-treat cancers, we too might be a bit cautious. But this is not the first time we have seen a strong connection between the use of aspirin and a reduced risk of serious cancers.

Skin Cancer and Lung Cancer:

Other studies have also found that aspirin use has been linked with a lower likelihood of developing squamous cell carcinoma of the skin as well as melanoma. A case-control study from China shows that women who took aspirin twice a week for at least a month were nearly 50 percent less likely to be diagnosed with lung cancer. That was among non-smokers. Among women who smoked, the reduction was 62 percent.

Colon Cancer:

An aspirin study from the Netherlands suggests that aspirin may actually improve survival in patients with colon cancer. Almost 4,500 people were included in the study that spanned nearly a decade. Of these, almost one in four took aspirin after their cancer diagnosis. Half had already been taking aspirin before the diagnosis and continued taking their low-dose aspirin pill after beginning treatment. One quarter of the colon cancer patients did not take aspirin. The researchers found that taking a baby aspirin pill daily reduced the risk of dying from colon cancer by up to 30 percent over the course of the decade.

A report published in the Journal of the National Cancer Institute showed that people taking daily aspirin were 40% less likely to develop digestive tract cancers. Over 100,000 American senior citizens were tracked for 10 years.

Liver Cancer:

A ten-year study of more than 300,000 individuals between 50 and 71 at the outset has demonstrated that aspirin use is associated with less liver cancer and even death from liver disease. People who took non-aspirin anti-inflammatory drugs like ibuprofen and naproxen had a one-third lower likelihood of liver cancer, but were just as likely as people not taking pain relievers to die from liver disease. Those taking aspirin, on the other hand, had a 37 percent lower risk of liver cancer and cut their risk of dying from liver disease in half.

Multiple Cancers:

When researchers review lots of aspirin trials, they come up with the same result over and over. An analysis involving more than 50 clinical trials was designed to determine if aspirin could prevent heart attacks and strokes. Nearly 80,000 subjects were included, and those assigned to take aspirin had 15 percent fewer deaths from cancer. They also experienced protection from heart attacks and strokes.

Another analysis covered 17,000 participants taking 75 mg of aspirin in randomized controlled trials. In this group of people, aspirin reduced the risk of metastasis by about 36 percent. This inexpensive drug appears to offer protection against cancers of the esophagus, breast, lung and stomach as well as against colon cancer. The scientists also found that, although aspirin can increase the risk of internal bleeding, this danger tends to fade somewhat with time and did not outweigh the cancer-protection benefit.

Even with all this good news about aspirin vs. cancer, there are a lot of clinicians who cannot bring themselves to say that aspirin could be a valuable anti-cancer drug. They point out that aspirin causes digestive tract upset and can lead to bleeding ulcers and that can be a life-threatening situation. They are not wrong that aspirin can be dangerous for some people.

Other Aspirin Benefits:

Aspirin has other potential benefits. Although it is no longer recommended routinely to prevent heart attacks in otherwise healthy people, there is evidence that it can be helpful for those at high risk. That would include people who have had a heart attack.

Doctors have also known for decades that aspirin can be helpful against pre-eclampsia. This is a dangerous complication during pregnancy that can cause hypertension, headaches and kidney damage. It is extremely dangerous for both mother and baby. Doctors often recommend low-dose aspirin after the 12^th week for high-risk patients. Of course this must always be approved and supervised by an obstetrician!

There will almost assuredly be new discoveries involving aspirin, but it is also important to recognize that aspirin poses risks when taken for long periods of time. Bleeding ulcers and bleeding strokes can be potentially life-threatening complications of regular aspirin use. Aspirin can also interact with many other medications, especially anticoagulants.

No one should ever undertake long-lasting treatment with aspirin, even in low doses, without first checking with a physician. Medical supervision is essential. We only wish modern medicine would appreciate the value of this very old and inexpensive medicine.
For our *FREE* guide to Key Aspirin Information click here.

Share your own experience with aspirin in the comment section. We would like to learn about both positive and negative stories, so please let us know how you have fared with this very old drug. Thank you for supporting The People’s Pharmacy!