Aspirin might reduce the incidence of pancreatic cancer: A meta-analysis of observational studies

Although there is evidence that non-steroidal anti-inflammatory drugs (NSAIDs) might be able to prevent pancreatic cancer, the findings from epidemiological studies have been inconsistent. In this paper, we conducted a meta-analysis of observational studies to examine this possibility. We searched PubMed and Embase for observational (cohort or case-control) studies examining the consumption of aspirin and other NSAIDs and the incidence of or mortality rates associated with pancreatic cancer. Twelve studies including approximately 258,000 participants in total were analysed. The administration of aspirin significantly reduced the incidence of pancreatic cancer (8 studies; odds ratio (OR) = 0.77; 95% confidence interval (CI) = 0.62 to 0.96; I2 = 74.2%) but not the mortality associated with it (2 studies; OR = 0.94; 95% CI = 0.73 to 1.22). Specifically, frequent aspirin use was associated with reduced pancreatic cancer incidence (OR = 0.57; 95% CI = 0.39 to 0.83 for high frequency; OR = 0.57; 95% CI = 0.38 to 0.84 for medium frequency). The summary ORs regarding the incidence of pancreatic cancer and either non-aspirin NSAIDs use (OR = 1.08; 95% CI = 0.90 to 1.31) or overall NSAIDs use (OR = 0.97; 95% CI = 0.86 to 1.10) were not significant. In conclusion, aspirin use might reduce the incidence of pancreatic cancer; however, this finding should be interpreted with caution because of study heterogeneity.


Supplementary
NA Eligibility criteria 6 Specify study characteristics (e.g., PICOS, length of follow-up) and report characteristics (e.g., years considered, language, publication status) used as criteria for eligibility, giving rationale.

Methods
Information sources 7 Describe all information sources (e.g., databases with dates of coverage, contact with study authors to identify additional studies) in the search and date last searched.

Methods
Search 8 Present full electronic search strategy for at least one database, including any limits used, such that it could be repeated.

Methods
Study selection 9 State the process for selecting studies (i.e., screening, eligibility, included in systematic review, and, if applicable, included in the meta-analysis).

Methods
Data collection process 10 Describe method of data extraction from reports (e.g., piloted forms, independently, in duplicate) and any processes for obtaining and confirming data from investigators.

Data items 11
List and define all variables for which data were sought (e.g., PICOS, funding sources) and any assumptions and simplifications made.

Risk of bias in individual studies
12 Describe methods used for assessing risk of bias of individual studies (including specification of whether this was done at the study or outcome level), and how this information is to be used in any data synthesis.

Summary measures
13 State the principal summary measures (e.g., risk ratio, difference in means). Methods

Synthesis of results
14 Describe the methods of handling data and combining results of studies, if done, including measures of consistency (e.g., I 2 ) for each meta-analysis.

Methods
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Section/topic # Checklist item Reported on page #
Risk of bias across studies 15 Specify any assessment of risk of bias that may affect the cumulative evidence (e.g., publication bias, selective reporting within studies).

Methods
Additional analyses 16 Describe methods of additional analyses (e.g., sensitivity or subgroup analyses, meta-regression), if done, indicating which were pre-specified.

Study selection
17 Give numbers of studies screened, assessed for eligibility, and included in the review, with reasons for exclusions at each stage, ideally with a flow diagram.

Results
Study characteristics 18 For each study, present characteristics for which data were extracted (e.g., study size, PICOS, follow-up period) and provide the citations.

Risk of bias within studies 19 Present data on risk of bias of each study and, if available, any outcome level assessment (see item 12). Results
Results of individual studies 20 For all outcomes considered (benefits or harms), present, for each study: (a) simple summary data for each intervention group (b) effect estimates and confidence intervals, ideally with a forest plot.

Risk of bias across studies 22 Present results of any assessment of risk of bias across studies (see Item 15). Results
Additional analysis 23 Give results of additional analyses, if done (e.g., sensitivity or subgroup analyses, meta-regression [see Item 16]). Results

DISCUSSION
Summary of evidence 24 Summarize the main findings including the strength of evidence for each main outcome; consider their relevance to key groups (e.g., healthcare providers, users, and policy makers).

Discussion
Limitations 25 Discuss limitations at study and outcome level (e.g., risk of bias), and at review-level (e.g., incomplete retrieval of identified research, reporting bias).

Discussion
Conclusions 26 Provide a general interpretation of the results in the context of other evidence, and implications for future research. Discussion

FUNDING
Funding 27 Describe sources of funding for the systematic review and other support (e.g., supply of data); role of funders for the systematic review. For more information, visit: www.prisma-statement.org.