Table 1. Details of published randomised double-blind placebo-controlled trials of folic acid for prevention of colorectal adenoma recurrence.
|
Intervention
|
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|---|---|---|---|---|---|---|---|---|---|
| Placebo | Folic acid | ||||||||
| Study | Yeara | Country | Folic acid dose (μg/day) | Duration (years) | N b | Outcome | N outcome/ total (%) | N outcome/ total (%) | RR (95%CI)c |
| Paspatis et al | NS | Greece | 1000 | 1 | 60 | Adenoma incidence | 11/29 (38) | 7/31 (23) | 0.48 (0.13–1.68)d |
| 2 | 60 | Adenoma incidence | 8/29 (28) | 4/31 (13) | 0.39 (0.08–1.72)d | ||||
| Cole et al | 1994–98 | USA | 1000 | 3 | 987 | Any adenoma incidence | 206/486 (42.4) | 221/501 (44.1) | 1.04 (0.90–1.20) |
| Advanced adenoma incidencee | 42/486 (8.6) | 57/501 (11.4) | 1.32 (0.90–1.92) | ||||||
| No of adenomas 1–2 | 168/486 (34.6) | 174/501 (34.7) | 1.00 (0.85–1.19) | ||||||
| ⩾3 | 38/486 (7.8) | 47/501 (9.4) | 1.20 (0.80–1.81) | ||||||
| 6–8 | 607 | Any adenoma incidence | 113/304 (37.2) | 127/303 (41.9) | 1.13 (0.93–1.37) | ||||
| Advanced adenoma incidencee | 21/304 (6.9) | 35/303 (11.6) | 1.67 (1.00–2.80) | ||||||
| No of adenomas 1–2 | 100/304 (32.9) | 97/303 (32.0) | 0.97 (0.77–1.22) | ||||||
| ⩾3 | 13/304 (4.3) | 30/303 (9.9) | 2.32 (1.23–4.35) | ||||||
| Logan et al | 1997–2001 | UK | 500 | 3 | 853 | Any adenoma incidence | 105/421 (24.9) | 115/432 (26.6) | 1.07 (0.85–1.34) |
| Advanced adenoma incidencee | 52/421 (12.4) | 52/432 (12.0) | 0.98 (0.68–1.40) | ||||||
a
Time period of participant recruitment.
b
Number of subjects available for outcome assessment.
c
Relative risk and 95% confidence interval.
d
Calculated from published raw data.
e
Advanced adenoma defined as adenomas ⩾1 cm in diameter, adenomas with villous or tubulovillous histology, adenomas with severe dysplasia, or diagnosis of colorectal cancer; NS, not stated.