In 2016, the US Preventive Services Task Force (USPSTF) recommended aspirin for the prevention of colorectal cancer in patients with certain cardiovascular risk profiles.1
The recommendation made aspirin the first pharmacologic agent endorsed for cancer prevention in individuals who were not at high risk for cancer.2 However, it hasn’t been clear if aspirin can provide risk-reducing benefits for other cancers.
A recent study suggests aspirin may lower the risk for gastric adenocarcinoma in women but not in men. The findings were published in Cancer Prevention Research3 and discussed in an AACR Virtual Journal Club presentation by Andrew T. Chan, MD, of Massachusetts General Hospital in Boston.4
Dr Chan noted that gastric cancer is the fifth most common form of cancer and the third leading cause of cancer death worldwide. As gastric cancers are generally discovered when cure is not possible, novel, tolerable, inexpensive, and scalable preventive strategies are a high priority.
A meta-analysis of 24 case-control studies suggested that aspirin and other nonsteroidal anti-inflammatory drugs (NSAIDS) reduced the risk for gastric cancer diagnosis by 22% (risk ratio, 0.78; 95% CI, 0.72-0.85).5 The magnitude of benefit was generally greater when NSAIDs were taken several times weekly and for longer than 5 years.
However, the optimal dosage and duration of aspirin use, including its relative benefit for specific subgroups (especially non-Asian populations), remain unclear.
To address the aforementioned issues, Dr Chan and colleagues analyzed data from 2 large, prospective US cohort studies — the Nurses’ Health Study (NHS) and the Health Professionals Follow-up Study (HPFS).3,4 The studies included data for 109,684 female nurses and 49,432 male health professionals, respectively.
At baseline and every 2 years, participants in both studies completed questionnaires asking about lifestyle factors, medical history, and disease outcomes. The baseline questionnaire was returned in 1980 for the NHS and 1986 for the HPFS, and participants in both studies were followed through 2014.
The median age of the cohort at the midpoint of follow-up (1996) was 61-64 years. More than 90% of participants were White, the mean body mass index was 27-27 kg/m2, and smoking history was consistent with population trends.
Use of aspirin and other agents was ascertained at each biennial assessment, except in 1986. At various time points between 1980 and 2014, participants were asked specifically about the number of aspirin tablets per week, the dosage of aspirin used, and the use of baby aspirin.
For participants who developed cancer, investigators reviewed source documents, including autopsy reports when available. In both studies, the follow-up rate exceeded 90%, and cases of gastric cancer were validated with very high concordance, Dr Chan said.
The investigators assessed aspirin’s association with gastric cancer development separately for men and women.
There were 316 documented cases of gastric adenocarcinoma: 176 in women and 140 in men. Cases of gastric cancer that did not have adenocarcinoma histology were excluded.
In a multivariate analysis (adjusted for age, race, lifestyle factors, etc.), taking aspirin at least twice a week was associated with a lower risk of gastric adenocarcinoma in women (hazard ratio [HR], 0.52; 95% CI, 0.37-0.73) but not in men (HR, 1.08; 95% CI, 0.77-1.52).
Dose trends showed the greatest benefit in women who took the most aspirin tablets weekly. Compared with women taking fewer than 0.5 tablets weekly, the HR was 0.51 for those taking 5 or more tablets weekly, 0.71 for those taking 1.5-4 tablets weekly, and 0.72 for those taking 0.5-1.4 tablets weekly (P for trend =.01).
Duration of aspirin use seemed to make a difference as well. Women who took aspirin for at least 10 years had the largest reduction in gastric adenocarcinoma risk (HR, 0.45; P <.001). Shorter-term aspirin use did not reduce the likelihood of developing gastric cancer.
In women, the data were consistent with previously observed aspirin-associated reductions in risk for colorectal cancer, suggesting that the development of gastrointestinal cancer, whether in the stomach, colon, or rectum, occurs over a protracted period, Dr Chan said.