Pretreatment age and serum lactate dehydrogenase as predictors of synchronous second primary cancer in patients with nasopharyngeal carcinoma

Objectives: Nasopharyngeal carcinoma (NPC) is a common cancer and is treated primarily by chemotherapy and radiotherapy. However, NPC with synchronous second primary cancer (SSPC) is very rare and its risk factors, treatment and prognosis remain unclear. In this study, we aimed to analyze patients with NPC and SSPC, and attempt to find potential predictors for these patients. Materials and methods: We retrospectively collected 681 patients with NPC from 2006 to 2018. Patients in this study were divided into two groups: those patients with SSPC and those without SSPC. We then analyzed the demographic data and survival of these two groups. Independent predictors of SSPC were determined by multivariate regression analysis. A comprehensive review of the literature was also performed. Results: We identified 17 NPC patients with SSPC in our case series and 13 cases in the literatures, and the most common SSPC is lung (16.1%). In univariate analysis, NPC patients with SSPC had older age (P < 0.001) and higher serum lactate dehydrogenase (LDH) (P = 0.008), compared with those without SSPC. In multivariate analysis, old age (P = 0.001) and high serum LDH (P = 0.023) remained independent predictors of SSPC, and a predictive equation model was established. NPC patients with SSPC had a significantly lower 5-year disease-specific survival rate compared with patients without SSPC (34.0% vs. 77.6%, P < 0.001) Conclusion: This study demonstrated that pretreatment age and serum LDH were independent predictors for SSPC in NPC patients. These independent factors can be used for early detection, and better facilitate the design of more appropriate treatment by medical professionals.