Incidence of urological tumors in Down's syndrome: a systematic review and meta-analysis.

BACKGROUND: Some authors have estimated that the incidence of testicular germ cell tumors in individuals with trisomy 21 is more than fivefold higher than that in the general population. OBJECTIVE: This systematic review aimed to estimate the incidence of urological tumors in patients with Down's syndrome. STUDY DESIGN: We conducted a search strategy in MEDLINE (OVID), EMBASE, LILACS, and the Cochrane Central Register of Controlled Trials (CENTRAL) from inception to nowadays. We assessed the risk of bias and performed a meta-analysis. Also, the heterogeneity between trials was evaluated by the I2 test. We completed the subgroup analysis based on the type of urological tumor (testis, bladder, kidney, upper urological tract, penile, retroperitoneum). RESULTS: We found 350 studies by the search strategy. After carefully reviewing, full-text studies were included. 16,248 individuals with Down's syndrome were included, and 42 patients presented with urological tumors. There was a total incidence of 0.1%, 95%CI (0.06-0.19), I2 61%. The most common urological tumor reported was testicular. We found six studies describing 31 events and an overall incidence of 0.19%, 95%CI (0.11-0.33), I2: 51%. Other studies reported kidney, penile, upper urinary tract, bladder, and retroperitoneum tumors with a very low incidence, 0.02%, 0.06%, 0.03%, 0.11%and 0.07%, respectively. DISCUSSION: Regarding non-testicular urological tumors, we found incidences as low as 0.02% in kidney cancer or 0.03% in the upper-urothelial tract tumors. It is also lower than the general population. Compared to the age of onset of patients, it is also lower than the general population, perhaps related to a shorter life expectancy. As a limitation, we found a high heterogeneity and a lack of information regarding non-testicular tumors. CONCLUSION: There was a very low incidence of urological tumors in people with Down's syndrome. Testis tumor was the most frequently described in all cohorts and within a normal distribution range.