This systematic review and meta-analysis evaluated the available evidence on the risk of metachronous advanced neoplasia (AN) and colorectal cancer (CRC) in patients with 3–4 nonadvanced adenomas (NAAs).
We searched MEDLINE, EMBASE, and Cochrane Library databases up to January 2021 for studies evaluating metachronous AN and CRC risk by comparing 3 groups (1–2 vs 3–4 vs ≥5 NAAs) at index colonoscopy. The estimates for risk of metachronous AN and CRC were evaluated using random-effects models.
Fifteen studies (n = 36,375) were included. The risk of metachronous AN was significantly higher in the 3–4 NAAs group than in the 1–2 NAAs group (relative risk [RR] 1.264, 95% confidence interval [CI] 1.053–1.518, P = 0.012; I2 = 0%); there was no difference between the ≥ 5 NAAs and 3–4 NAAs groups (RR 1.962, 95% CI 0.972–3.958, P = 0.060; I2 = 68%). The risks of metachronous CRC between the 1–2 NAAs and 3–4 NAAs groups (RR 2.663, 95% CI 0.391–18.128, P = 0.317; I2 = 0%) or the 3–4 NAAs and ≥ 5 NAAs groups (RR 1.148, 95% CI 0.142–9.290, P = 0.897; I2 = 0%) were not significantly different.
Although the risk of metachronous AN was greater in the 3–4 NAAs group than in the 1–2 NAAs group, the risk of metachronous AN and CRC between the 3–4 NAAs and ≥ 5 NAAs groups was not different. This suggests that further studies on metachronous AN and CRC risk in the 3–4 NAAs group are warranted to confirm a firm ≥5-year interval surveillance colonoscopy.