Evidence from laboratory studies suggests that aspirin and tea polyphenols may have an antineoplastic effect in esophageal squamous cell carcinoma (ESCC). To assess the safety and efficacy of aspirin and tea polyphenols for preventing ESCC, the investigators designed this double-blind, randomized controlled clinical trial. Research project is planned to recruit 10,000 participants with the ages of 40-60 years in Fengfeng city, Hebei province, China, which has been known as a high incidence region of ESCC. All the participants receive endoscopic examination. Lugol's chromoendoscopy is used to identify esophageal unstained lesions (USLs). The location and size of each USL will be recorded followed by collecting biopsy samples from each USL. Participants with USL are randomly assigned to receive 100 mg/d of aspirin (n=200), 100 mg/d of tea polyphenols (n=200), or placebo (n=200) for six months. Follow-up consists of 2 endoscopic surveillance cycles (the first interval will be at six months and the second at 3 or 5 years later). The primary outcome measure was occurrence of high grade dysplasia and invasive ESCC. Secondary outcome was the mortality of the participants and adverse events.

Inclusion Criteria:

1. age 40 to 60 years;
2. Lugol's chromoendoscopy showing at least one USL 1 cm or larger containing mild to moderate dysplasia and chronic inflammation;
3. subject neither pregnant nor intending to become pregnant during the study.

Exclusion Criteria:

1. current non-steroidal anti-inflammatory drugs (NSAID) therapy;
2. major intercurrent illness;
3. pregnancy;
4. invasive carcinoma;
5. any condition that could be worsened by aspirin or tea polyphenols.