Aspirin, Colorectal Cancer, and Oncology: A Comprehensive Analysis of Recent Research
Recent research conducted by Harvard scientists has brought to light the significant role that aspirin can play in reducing the risk of colorectal cancer, particularly for individuals with unhealthy lifestyles. This groundbreaking study analyzed 30 years of data collected from 100,000 healthcare workers, revealing that regular aspirin use is associated with a one-third decrease in colon cancer risk among those with a low ‘healthy lifestyle score.’ This score is a metric designed to quantify five lifestyle factors that increase the risk of colorectal cancer, including smoking, alcohol use, unhealthy diet, lack of exercise, and high body mass index (BMI). The lead author of the study, Dr. Andrew Chan, emphasizes that this research highlights specific lifestyle factors that can put people at risk for colorectal cancer and shows that aspirin can help reverse those risk factors.
The potential benefits of aspirin in cancer prevention have been emerging over the last two decades. The initial observations began in the 1980s when researchers noticed that patients with arthritis who took aspirin had lower rates of cancer. This led to randomized studies in the early 2000s that compared cancer rates between people prescribed aspirin and those given a placebo. These studies consistently showed that individuals taking aspirin had a lower risk of developing pre-cancerous colon polyps. In 2016, the US Preventive Services Task Force recommended that individuals aged 50 to 59 take aspirin regularly to prevent both heart disease and colorectal cancer. However, this recommendation was reversed in 2022 due to concerns about side effects such as bleeding, underscoring the need for more targeted research to determine who would benefit most from aspirin use.
Colorectal cancer remains the second leading cause of cancer deaths in the United States, and its incidence is on the rise among younger populations for reasons that are not yet well understood. To conduct their study, Harvard researchers analyzed data from two longitudinal studies: one involving 121,700 female nurses aged 30 to 55, and another including 51,519 male health professionals aged 40 to 75. Over a 30-year period, participants provided lifestyle information through biennial questionnaires. The studies revealed that all five lifestyle factors (diet, smoking, alcohol use, exercise, BMI) were linked to the risk of colorectal cancer. Participants were divided into two groups—those who did not take aspirin regularly and those who took a standard dose of two 325 mg aspirin tablets a week (equivalent to a baby aspirin a day).
The research did not assess the risks associated with aspirin or the ‘cost-benefit’ ratio for any individual, highlighting that the decision to take aspirin should be made on a case-by-case basis by healthcare professionals. This caution is particularly relevant given the potential side effects of aspirin, such as gastrointestinal bleeding. Despite these concerns, the findings suggest that aspirin could serve as a valuable preventive measure against colorectal cancer, especially for those with unhealthy lifestyles. The study found that people with unhealthy habits saw the greatest benefit from aspirin usage, experiencing an 18% lower risk of developing colorectal cancer compared to non-users.
Aspirin’s ability to inhibit pro-inflammatory signals that can lead to cancer is one of the key mechanisms through which it may reduce colorectal cancer risk. However, more research is needed to fully understand the various ways aspirin may prevent cancer. For instance, aspirin may also aid the immune system in targeting cancer cells, reduce inflammation—a known risk factor for colorectal cancer—and promote the growth of beneficial gut bacteria. These multifaceted benefits make aspirin a promising candidate for cancer prevention, but the potential downsides, such as increased bleeding risk, cannot be ignored.
Mass General Brigham conducted another study on the effects of aspirin on reducing the risk of colorectal cancer in adults with unhealthy lifestyles. This study included 108,000 health professionals around 50 years old, who were assigned a lifestyle score based on factors such as body mass index, alcohol consumption, physical activity, diet, and smoking habits. Regular aspirin use was defined as two or more standard tablets or six or more low-dose pills per week. Over three decades, 2,500 cases of colorectal cancer were documented. Those with unhealthier lifestyles, particularly if they were overweight or heavy smokers, benefitted the most from aspirin use compared to their healthier peers.
The findings published in JAMA Oncology indicate that aspirin can lower the risk of colorectal cancer in individuals with multiple risk factors. For example, unhealthy participants had a 3.4% chance of getting colorectal cancer if they did not regularly take aspirin, compared to a 2.1% chance if they did. In contrast, the rates of colorectal cancer were 1.5% in the aspirin-taking group and 1.6% in the non-aspirin group among the healthiest participants. This suggests that while aspirin can be beneficial for those with unhealthy lifestyles, its impact is less significant for those who already maintain healthy habits.
The US Preventive Services Task Force’s initial recommendation in 2016 for daily low-dose aspirin for adults in their 50s aimed to prevent heart disease and colorectal cancer. However, this guidance was amended in 2022 due to research showing that older individuals who took a daily low dose of aspirin had an increased risk of advanced cancer and death. The task force now recommends that people aged 40 to 59 who are at higher risk for heart disease discuss with their doctor whether they should take aspirin. This nuanced approach reflects the complex balance between the benefits and risks of aspirin use, particularly for older adults.
New research from Massachusetts General Hospital in Boston further supports the notion that aspirin is most effective for those with lifestyles that increase their risk for colon cancer. The study examined data from nearly 108,000 participants and found that those with unhealthy lifestyles who regularly took aspirin had a lower risk of developing colon cancer. This is likely because aspirin can decrease the production of pro-inflammatory proteins, which can lead to tumor development. However, the study did not track the risk of bleeding, a common side effect of aspirin, suggesting that healthcare providers should carefully weigh the benefits and risks when recommending aspirin to patients.
The analysis revealed that over a 10-year period, the rate of colon cancer was lower among regular aspirin users compared to non-users. When ranked by lifestyle, those with unhealthy habits saw a larger difference in colon cancer rates between regular aspirin users and non-users. In contrast, there was no significant difference in colon cancer rates among those with the healthiest lifestyles. This indicates that while aspirin can be a valuable preventive measure for some, it should not be seen as a substitute for a healthy lifestyle.
Another study led by researchers at Mass General Brigham and published in JAMA Oncology sought to identify individuals who would benefit most from aspirin usage. The study analyzed health data from over 100,000 participants in the Nurses’ Health Study and Health Professionals Follow-up Study. Regular aspirin use was defined as two or more standard dose (325 mg) tablets per week or daily low-dose (81 mg) aspirin. The study participants were followed starting at an average age of 49.4 years. The 10-year cumulative incidence of colorectal cancer was 1.98% for those who took aspirin regularly, compared to 2.95% for those who did not.
The greatest benefit of aspirin was seen in those with the unhealthiest lifestyles. The group with the lowest healthy lifestyle scores had a 3.4% chance of getting colorectal cancer without regular aspirin use, compared to a 2.12% chance with aspirin use. In contrast, in the healthiest group, the rates were 1.5% for those who took aspirin regularly and 1.6% for those who did not. This means that in the least healthy group, treating 78 patients with aspirin could prevent one case of colorectal cancer over a 10-year period, compared to 909 patients for the healthiest group. These findings suggest that healthcare providers may want to consider recommending aspirin more strongly to patients with less healthy lifestyles.
However, the study did not assess potential side effects of daily aspirin use, such as bleeding. While the study controlled for various risk factors, there may have been additional factors that influenced the findings. Despite these limitations, the research provides compelling evidence that aspirin can significantly reduce the risk of colorectal cancer in individuals with unhealthy lifestyles. As such, healthcare providers should consider these findings when advising patients on preventive measures for colorectal cancer.