Table 2 Standardised incidence ratios (SIRs) and their 95% confidence intervals (CI) for anal and colorectal cancer among patients with benign inflammatory anal lesions and haemorrhoids, by duration of follow up.
| Inflammatory lesions* | Haemorrhoids | |||||||
|---|---|---|---|---|---|---|---|---|
| Anal cancer | Colorectal cancer† | Anal cancer | Colorectal cancer† | |||||
| Obs | SIR (95% CI) | Obs | SIR (95% CI) | Obs | SIR (95% CI) | Obs | SIR (95% CI) | |
| <1 y | 6 | 24.0 (8.8–52.3) | 71 | 3.9 (3.0–4.9) | 11 | 14.9 (7.5–26.7) | 200 | 3.6 (3.1–4.1) |
| 1–4 y | 8 | 8.3 (3.6–16.3) | 88 | 1.3 (1.0–1.6) | 2 | 0.7 (0.1–2.5) | 228 | 1.1 (0.9–1.2) |
| 1 y | 4 | 16.3 (4.4–41.7) | 21 | 1.2 (0.7–1.8) | 2 | 2.8 (0.3–9.9) | 68 | 1.3 (1.0–1.6) |
| 2 y | 3 | 12.3 (2.6–36.1) | 22 | 1.3 (0.8–1.9) | 0 | – | 55 | 1.0 (0.8–1.3) |
| 3–4 y | 1 | 2.1 (0.05–11.7) | 45 | 1.4 (1.0–1.8) | 0 | – | 105 | 1.0 (0.8–1.2) |
| 5–9 y | 6 | 5.4 (2.0–11.7) | 97 | 1.3 (1.0–1.5) | 6 | 1.8 (0.7–3.9) | 243 | 1.0 (0.9–1.1) |
| 10+ y | 6 | 2.6 (1.0–5.7) | 180 | 1.1 (0.9–1.3) | 8 | 1.3 (0.6–2.5) | 509 | 1.1 (1.0–1.1) |
| 10–14 y | 2 | 2.2 (0.3–7.9) | 75 | 1.2 (0.9–1.5) | 3 | 1.1 (0.2–3.3) | 189 | 1.0 (0.8–1.1) |
| 15–19 y | 2 | 2.9 (0.4–10.6) | 56 | 1.2 (0.9–1.5) | 4 | 2.2 (0.6–5.6) | 145 | 1.0 (0.9–1.2) |
| 20+ y | 2 | 2.8 (0.3–10.2) | 49 | 0.9 (0.7–1.2) | 1 | 0.6 (0.01–3.0) | 175 | 1.2 (1.0–1.4) |
| 3–37 y | 13 | 3.3 (1.8–5.7) | 322 | 1.2 (1.1–1.3) | 14 | 1.3 (0.7–2.1) | 857 | 1.0 (1.0–1.1) |
*Benign inflammatory anal lesions included anal fissure, fistula, and perianal abscess.
†Excluding anal cancer.
Obs, observed.