Baseline characteristics of the intention-to-treat population of patients
| Aspirin 160 mg/day (N=73) | Aspirin 300 mg/day (N=67) | Placebo (N=132) | Total (N=272) | |
| Mean±SD age (years) | 59±9 | 56±9 | 57±10 | 58±10 |
| Sex | ||||
| Male | 51 (70%) | 48 (72%) | 92 (70%) | 191 (70%) |
| Female | 22 (30%) | 19 (28%) | 40 (30%) | 81 (30%) |
| Mean±SD BMI (kg/m2) | 26±3.5 | 26.2±3.4 | 25.7±4 | 25.9±3.6 |
| Tobacco use | ||||
| Current smokers | 11 (15%) | 19 (28%) | 34 (26%) | 64 (23.5%) |
| Smokers with >20 pack-years | 17 (23%) | 15 (22%) | 22 (17%) | 54 (20%) |
| Family history of colorectal cancer | 26 (36%) | 25 (37%) | 42 (32%) | 93 (34%) |
| Location (number of polyps) | ||||
| Distal colon | 67 (145) | 56 (111) | 106 (213) | 229 (469) |
| Proximal colon | 16 (26) | 17 (25) | 36 (61) | 69 (112) |
| Patients with only one polyp | 34 (47%) | 31 (46%) | 62 (47%) | 127 (47%) |
| Median number (range) of polyps/patient | 2 (1–8) | 1.5 (1–9) | 2 (1–9) | 2 (1–9) |
| Median size (range) of polyps (mm) | 6 (1–50) | 6 (1–60) | 5 (1–50) | 6 (1–60) |
| Median (range) polyp burden/patient (mm) | 16 (2–108) | 17 (3–70) | 17 (2–117) | 16 (2–117) |
| Nature (number of polyps) | ||||
| Adenomatous | 67 (135) | 60 (122) | 115 (237) | 242 (494) |
| Hyperplastic | 11 (29) | 7 (12) | 18 (22) | 36 (63) |
| Other | 4 (4) | 2 (2) | 5 (8) | 11 (14) |
| Archetype (number of polyps) | ||||
| Tubulous | 44 (81) | 40 (65) | 77 (158) | 161 (304) |
| Tubulovillous | 31 (38) | 29 (44) | 51 (67) | 111 (149) |
| Villous | 2 (3) | 2 (2) | 3 (3) | 7 (8) |
| Adenomas ≥10 mm (number of polyps)* | 49 (62) | 45 (54) | 71 (86) | 165 (202) |
| Adenomas with high-grade dysplasia (number of polyps) | 8 (9) | 17 (18) | 18 (23) | 43 (50) |
| Advanced adenomas (number of polyps) | 53 (73) | 49 (72) | 82 (116) | 184 (261) |
↵* Statistically significant difference between aspirin (both doses grouped) and placebo. Except when specifically mentioned, numbers within brackets represent the numbers of polyps. Advanced adenomas are defined as villous or tubulovillous adenomas and/or size >10 mm and/or high-grade dysplasia.
BMI, body mass index.