Second primary malignancy in patients with cholangiocarcinoma: a population-based study.

Background: A population-based estimate of risk of second primary malignancy (SPM) patients with cholangiocarcinoma (CCA) is still lacking. Objectives: To investigate the overall and site-specific risk of SPM in patients with CCA. To identify risk factors of SPM and further evaluate the impact of SPM on overall survival (OS) and disease specific survival (DSS) in patients with CCA. Methods: Patients with histologically diagnosed CCA between 1973 and 2015 were identified from the Surveillance, Epidemiology and End Results database. Standardized incidence ratio (SIR) was calculated. Risk factors for SPM and CCA survival were evaluated by logistic, Cox, and nomogram methods. Results: We found that the overall risk of SPM in patients with CCA was significantly higher than that in the general population (SIR =1.27, 95% CI =1.03-1.55, P<0.05). The risk of SPM was significantly increased at specific sites, including transverse colon, intrahepatic bile duct, other biliary, and thyroid. A significant increase in overall risk was characterized in the subgroups of patients aged <= 29, patients aged 30-59 years, females, whites, and patients with latency <= 11 months (63.41, 2.45, 1.4, 1.3, and 2.6-fold, respectively). In patients with CCA, not having undergone surgery for the first primary malignancy (vs having undergone surgery for the first primary malignancy; HR =0.269; 95% CI =0.211 -0.342; P<0.001) was associated with significantly decreased risk of SPM. Patients with SPM had better OS and DSS than those without SPM (Log rank <0.001). Absence of SPM was an independent risk factor for poorer OS and DSS. Conclusion: Although the risk of SPM in patients with CCA was significantly increased, the presence of SPM did not shorten OS and DSS of patients with CCA, possibly due to the relatively poorer survival of patients with CCA.