Effectiveness of Low Dose Aspirin in Decreasing the Chance Getting Stomach and Intestine Cancer

Study Overview
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Brief Summary
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In this study, researchers wanted to learn more about the effect of Aspirin taken as low dose (75 - 300 mg) in preventing stomach, colorectal and esophagus cancer. The researchers were interested in the effect by duration of aspirin use and the effect on the time since aspirin intake has been stopped in preventing stomach, colorectal and esophagus cancer. In addition, the study also looked into the time patients survived after being diagnosed (survival rate) with cancer and number of cancer patients who died (case fatality rate). The study was based on an electronic database managed by the Health Authority in Hong Kong containing anonymized clinical information of patients living in Hong Kong.

Official Title
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Effectiveness of Low-dose Aspirin in Gastrointestinal Cancer Prevention - Hong Kong

Conditions
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Gastrointestinal Cancer

Intervention / Treatment
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* Drug: Acetylsalicylic Acid (Aspirin, BAYE4465)


Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: - Received prescription of either low-dose aspirin (75-300 mg) or paracetamol monotherapy during enrolment period. Exclusion Criteria: Received prescription of aspirin monotherapy or combination one year prior to the index date Recorded diagnoses of any type of cancer before the index date Recorded procedures of colectomy, gastrectomy prior to the index date Age < 40 years

Ages Eligible for Study
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Minimum Age: 40 Years

Sexes Eligible for Study
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All

Accepts Healthy Volunteers
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No

Study Plan
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How is the study designed?
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Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| New-users of Low-dose aspirin (exposed group)<br>New-users of low-dose aspirin is defined as patients who did not receive any prescriptions of low-dose aspirin one year prior to the index date. | Drug: Acetylsalicylic Acid (Aspirin, BAYE4465)<br>* Follow clinical administration<br>|
| Users of Paracetamol (non-exposed group)<br>Users of Paracetamol is defined as patients who receive first prescription of paracetamol during the study period. Since the patients receiving low-dose aspirin are potentially less healthy compared to non-users of aspirin, patients receiving paracetamol as the control group can minimise healthy user bias. | |

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Incidence rate ratio of colorectal cancer among users of low-dose-aspirin (exposed) and users of paracetamol monotherapy (non-exposed) | Ratio of incidence (per 10,000 person years) among users of low-dose-aspirin (exposed) and users of paracetamol monotherapy (non-exposed) | Retrospective analysis between 1st January 2004 and 31st December 2008 | 
| Incidence rate ratio of gastric cancer among users of low-dose-aspirin (exposed) and users of paracetamol monotherapy (non-exposed) | Ratio of incidence (per 10,000 person years) among users of low-dose-aspirin (exposed) and users of paracetamol monotherapy (non-exposed) | Retrospective analysis between 1st January 2004 and 31st December 2008 | 
| Incidence rate ratio of esophageal cancer among users of low-dose-aspirin (exposed) and users of paracetamol monotherapy (non-exposed) | Ratio of incidence (per 10,000 person years) among users of low-dose-aspirin (exposed) and users of paracetamol monotherapy (non-exposed) | Retrospective analysis between 1st January 2004 and 31st December 2008 | 

Secondary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Duration of aspirin use | Minimum duration of aspirin use to confer the protective effects in preventing colorectal, gastric and esophageal cancer | Retrospective analysis between 1st January 2004 and 31st December 2008 | 
| Risk of colorectal, gastric and esophageal cancer after discontinuation of aspirin use | Logistic regression will be conducted based on nested case-control study with stratification on the recency of exposure with current use, past use, and distant use of aspirin. | Retrospective analysis between 1st January 2004 and 31st December 2008 | 
| Case-fatality and survival rate | For colorectal cancer, gastric or oesophageal | Retrospective analysis between 1st January 2004 and 31st December 2008 | 

 Terms related to the study
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Keywords Provided by Centre Hospitalier Valida
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Esophageal cancer, Gastric cancer, Colorectal cancer