Study: Frequent aspirin use may reduce the risk of ovarian cancer

IN-DEPTH REVIEW OF RESEARCH
Study background

Aspirin has been studied as a form of chemoprevention (medicine taken to prevent disease) for years. Researchers have asked whether aspirin is useful for both heart disease and cancer.

The effects of aspirin on cancer risk are mixed. Some evidence indicates that aspirin can help to prevent colon cancer. In the 2011 CAPP2 study, daily high-dose aspirin reduced colon cancer risk by 63 percent in people with Lynch syndrome. Follow-up research published in 2020 confirmed this benefit. A 2016 study showed that among people with an average risk of colon cancer, regular use of aspirin reduced their risk of colon cancer by 19 percent and any GI cancer by 15 percent.

Yet the news is not all good. The large 2020 ASPREE trial found that aspirin may cause harm. Participants ages 70 and over who took low-dose aspirin were as likely to develop cancer as those who did not take aspirin; however, their cancer was more likely to be advanced and result in death.

Recent studies also are looking for biomarkers to learn more about who might benefit from taking aspirin.

Researchers of this study wanted to know

The research team wanted to know if there was enough evidence to recommend that people with certain risk factors for ovarian cancer could benefit from taking aspirin daily.

Populations looked at in this study

This study looked at women from 17 studies who were at risk for ovarian cancer. Most were U.S.-based studies but some were conducted in the United Kingdom and Australia. The median age of participants ranged from 46 to 68.2 years in the nine cohort studies examined (see below). The median age of the participants in the case-control studies ranged from 56.2 to 60.7 years. The race or ethnicity of the people in the study samples was not reported.

Study design

The 17 studies included nine cohort studies from the Ovarian Cancer Cohort Consortium and eight population-based case-control studies from the Ovarian Cancer Association Consortium.

A cohort study follows a group of people over time. A case-control study compares a study group to a control group. Because these are two different types of data sets, the research team looked at them together and separately. The sample included 2,600 people with ovarian cancer in the cohort studies and 5,726 with ovarian cancer in the case-control studies.

Study findings

• Overall, aspirin was associated with a 13% reduction of ovarian cancer risk in this study.
  • Analysis of the cohort studies found a 10% reduction in risk; the case-control studies revealed a 16% reduction.
  • Notably, there was a 14% reduction in the risk of developing hard-to-treat, high-grade serous ovarian cancer.
• The reduction in risk was seen in people who were at higher risk due to obesity or had a family history of breast or ovarian cancer, a lack of oral contraceptive use, no prior pregnancies and no tubal ligation.
• This benefit was seen across the study groups regardless of risk with one exception. Women with endometriosis did not benefit from frequent aspirin use. It is possible that this was due to the relatively small number of people with endometriosis in the sample.
• The risk reduction was seen in both obese and nonobese women who took aspirin frequently. The benefit was numerically slightly higher among obese women (21% compared to 9%) but statistically it was the same. Obesity was defined by body mass index.
• The benefit extended to people with and without a family history of breast or ovarian cancer. The research team was not able to look at specific inherited mutations because they did not know the participants' genetic status.
• In the case-control studies, the investigators found a possible higher benefit of aspirin use as women aged, with the strongest benefit among women ages 70+ (18% reduction in risk). However, they did not find the same difference in the cohort studies.

Strengths and limitations

Strengths

• Many of the previously established studies, such as the Nurses’ Health Study and the Sister Study, follow large groups of people for many years and use high-quality research methods, which increases confidence in the conclusions. These studies have influenced what we know about healthy diet, exercise, prevention of chronic disease and related issues.
• Scientists and physicians from multiple institutions and specialties were involved in this research, indicating that the results can be generalized to people from different regions.

Limitations

• Although some studies included participants with a family history of cancer, researchers did not include genetic information on participants such as BRCA mutation or Lynch syndrome status. It is unclear whether people with inherited mutations that increase ovarian cancer risk would also benefit from frequent aspirin use.
• The research team was unable to look only at low-dose aspirin use, which has previously been associated with risk reduction. They noted that people who take aspirin frequently often take a lower dose, according to a correlation observed in prior research.
• The cohort studies were all conducted in the U.S. The case-control studies included participants from the U.S., the United Kingdom and Australia. No other countries were represented.
• The research team did not have data regarding when people in the study started taking aspirin or why.
• The results do not look at risk by race or ethnicity, so it is unclear if different groups would respond similarly.

Context

This study summarizes existing research from 17 studies on frequent aspirin use to prevent ovarian cancer. These study authors focused on the benefit of aspirin for people with certain ovarian cancer risk factors.

Aspirin is studied for ovarian cancer prevention due to the relationship between inflammation and this gynecologic cancer. Aspirin is an anti-inflammatory, and there is evidence that chronic inflammation may contribute to ovarian cancer. This potential relationship was first observed in studies of aspirin to prevent heart disease.

While very serious, ovarian cancer is not common. And despite the possible benefit of taking aspirin, it  also has drawbacks, most notably a higher risk of bleeding. For these reasons, doctors do not generally recommend taking aspirin to prevent ovarian cancer.

Yet, this study confirmed a potentially modest benefit of daily aspirin with a stronger reduction of risk for people with two or more risk factors for ovarian cancer. However, this approach needs to be balanced with other strategies to decrease risk, including risk-reducing surgery and oral contraceptive use.

Conclusions

These results confirm that taking aspirin frequently may help to prevent ovarian cancer, even more aggressive types of ovarian cancer. This is the first study to find that the benefit extends to people with specific risk factors.

The reduction in risk was seen in people at higher risk due to obesity, family history of breast or ovarian cancer, lack of oral contraceptive use, no prior pregnancies and no tubal ligation. The research team did not see a reduction in risk among people with endometriosis. Although this study showed the benefit of frequent aspirin use among people with a family history of breast or ovarian cancer, it did not specifically look at people with known BRCA mutations or Lynch syndrome.

Future research is needed to address whether people with different inherited mutations or from varied racial and ethnic backgrounds might benefit from taking aspirin. Additional research is also needed to determine the best dose of aspirin to use in this context.

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posted 2/22/23