Primary Sjogren's syndrome and malignancy risk: a systematic review and meta-analysis.

OBJECTIVE: To investigate the association between primary Sjogren's syndrome (pSS) and the risks of malignancy including overall malignancy and site-specific malignancies through a systematic review and meta-analysis. METHODS: We searched Pubmed before January 2013, with a restriction to English language publications. Studies were included if they met the following criteria: (1) a cohort or observational study; (2) pSS as one of the exposure interests; (3) cancer as an outcome of interest; (4) relative risk (RR) or standardised incidence rate (SIR) with 95% CIs. We used a random or fixed effects model to calculate the pooled RR according to the heterogeneity test. RESULTS: Fourteen studies involving more than 14 523 patients with pSS were included. Compared with the general population, patients with pSS had significantly increased risks of overall cancer (pooled RR 1.53; 95% CI 1.17 to 1.88), non-Hodgkin lymphoma (NHL) (pooled RR 13.76; 95% CI 8.53 to 18.99) and thyroid cancer (pooled RR 2.58; 95% CI 1.14 to 4.03). A significant association was found in various subgroup meta-analyses for NHL but, for overall malignancy, a significant association was only found in some groups. Additionally, the number of studies exploring the association of pSS with the risk of solid malignancies was so small that we could not carry out subgroup meta-analyses. CONCLUSIONS: This meta-analysis indicates that pSS is significantly associated with increased risks of overall malignancy, NHL and thyroid cancer. However, it is not yet known whether the apparent increased risk of overall malignancy in patients with pSS is due to the relatively high prevalence of NHL in that group.