For years, doctors have been debating the pros and cons of aspirin. They have long known that this old drug can cause serious gastrointestinal irritation. But epidemiologists have also noted that regular aspirin users appear to suffer fewer digestive tract cancers. Other research suggests aspirin may offer benefit against several different cancers. A new study published in the journal Cancer (April 22, 2024) offers an explanation for how aspirin may help prevent colorectal cancer.
Aspirin Use May Help Prevent Colorectal Cancer:
A meta-analysis concluded that regular aspirin use lowers the risk of colorectal cancer (Annals of Oncology, April 1, 2020). The investigators reviewed 45 observational studies published between January 2011 and March 2018. In addition, they considered 150 additional articles published in a prior meta-analysis. Sixty-six of these provided information on colorectal cancer risk and aspirin use.
When the scientists pooled the data from these 66 studies, they found that regular aspirin use seems to prevent colorectal cancer. The rate of this common malignancy dropped by nearly 30 percent among aspirin users.
In analyzing the eleven studies that provided data on aspirin dose, the researchers found that higher doses appeared more effective than lower doses. That is, people taking 75 mg of aspirin daily lowered their chance of cancer by about 10 percent, whereas those taking 500 mg a day reduced their risk by about 50 percent.
Pharmacologists call this a dose response curve. It is usually considered an important metric when establishing cause and effect.
Fast Forward to 2024:
The authors of the latest study in the journal Cancer point out that:
“Colorectal cancer (CRC) is the third most common cancer and the fourth most frequent cause of cancer deaths worldwide. Several studies have demonstrated that aspirin can play an important role in the chemoprevention of CRC.”
They go on to emphasize:
“In fact, many long-term follow-ups of randomized controlled trials of aspirin versus control have shown that daily aspirin use reduces incidence and mortality from CRC, after a latent period of approximately 8 to 10 years and total cancer mortality from 5 years to 20 years, with reductions in deaths from several other cancers.”
HOW Does Aspirin Prevent Colorectal Cancer (CRC)?
The latest research boils this process down to one sentence:
“These data suggested that regular aspirin use may have an active role in enhancing immunosurveillance against CRC.”
That may seem fairly simple, but trust us when we say that “immunosurveillance” is a very complex and multifactorial process. The idea that aspirin plays a “chemoprevention” role against colorectal cancer is impressive. The authors provide a great deal of detail about the “interrelated mechanisms” whereby aspirin prevents CRC cancer or metastatic disease.
The bottom line seems to be that aspirin helps the immune system seek out cancer cells and attack them. Aspirin also appears capable of limiting metastases or the spread of cancer, especially to lymph nodes.
Does Aspirin Use Lower the Risk of Other Cancers?
People who take aspirin daily develop head and neck cancers as often as people who don’t take it. However, aspirin may help protect users against esophageal cancer and possibly even pancreatic cancer. The researchers point out that longer use (at least five years) appears to offer more protection.
An “umbrella review” published in the journal Heliyon (Jan. 30, 2024) notes that NSAIDs, especially aspirin:
“…might be associated with a decreased risk of several cancers, including the central nervous system, breast, esophageal, gastric, head and neck, hepatocellular, cholangiocarcinoma, colorectal, endometrial, lung, ovary, prostate, and pancreatic cancers, but regular intake of any dose of non-aspirin NSAIDs (NA-NSAIDs) could increase the incidence of kidney cancer.”
As the scientists noted, however, the quality of evidence was “low” or “very low.” In addition, the authors also caution about “gastrointestinal reactions” and “contraindications.”
They go on to state that:
“…it is still too early to recommend that people with no disease regularly consume NSAIDs to prevent cancer.”
A systematic review and meta-analysis of prophylactic aspirin vs. breast cancer concluded (European Journal of Surgical Oncology, Oct. 2023):
“This meta-analysis found an association between aspirin intake and BC [breast cancer] risk reduction. A more favourable outcome was noted with ingestion of greater than 6 tablets of aspirin per week. Aspirin had a significant risk reduction in patients with ER [estrogen receptor] positive tumours compared to ER negative BC.”
Before people get overly enthusiastic about taking aspirin as a chemoprevention strategy, some words of caution. A systematic review and meta-analysis of randomized trials concluded that blood pressure medications (ACE inhibitors and ARBs), metformin for diabetes and nonsteroidal anti-inflammatory drugs (NSAIDs including aspirin) did not improve treatment or prevent recurrence of cancer (Cancer Medicine, March, 2024).
Should You Take Aspirin to Prevent Colorectal Cancer?
Aspirin can provoke serious intestinal irritation, including bleeding ulcers (World Journal of Gastroenterology, March 21, 2013). On the other hand, aspirin may help prevent recurrent heart attacks (Advances in Therapy, Aug. 2019). If one of your parents was diagnosed with colon or rectal cancer, you should talk with your doctor. You’ll need to examine your risk to decide whether to take aspirin to prevent colorectal cancer.
