Favorable survival of patients with nasopharyngeal carcinoma associated with metachronous multiple primary cancers: A retrospective study

Patients successfully treated for nasopharyngeal carcinoma (NPC) are at an increased risk of developing multiple primary cancers (MPCs), but the prognostic implications of synchronous (sMPC) vs. metachronous (mMPC) disease remain unclear. The present study aimed to compare the clinical characteristics and survival outcomes between patients with NPC with MPC, sMPC and mMPC, and to identify prognostic factors. Data from 306 patients with NPC-related MPC admitted to the First Affiliated Hospital of Guangxi Medical University (Nanning, China) from 2012 to 2023 were retrospectively analyzed, with 35 cases of sMPC (diagnosed within 6 months of the detection of the primary cancer) and 271 cases of mMPC (diagnosed >6 months apart). The clinical characteristics, treatment details and survival outcomes of patients were compared using the χ² test, Fisher's exact test, t-test, Kaplan-Meier method and multivariate Cox regression analysis. The results demonstrated that sMPC, compared with mMPC, was significantly associated with a higher proportion of other-cancer-first cases (37.1 vs. 11.8%; P<0.001), an older mean age (53.3±12.4 vs. 46.2±11.9 years; P=0.001), being a heavy smoker (11.4 vs. 3.0%; P=0.042) and advanced-stage first cancers (80.0 vs. 53.5%; P=0.002). The median survival duration for the first cancer was significantly shorter in patients with sMPC compared with those with mMPC (41.3 vs. 160.3 months; P<0.001). Multivariate analysis identified mMPC [adjusted hazard ratio (HR), 0.21; P<0.001], an older age at first diagnosis (adjusted HR, 1.04; P<0.001), advanced tumor-node-metastasis (TNM) stage (adjusted HR, 2.8; P<0.001) and radiotherapy for first cancer (adjusted HR, 0.55; P=0.042) as independent prognostic factors. NPC with mMPC was associated with longer survival than NPC with sMPC. Therefore, age, TNM stage and radiotherapy were identified as key prognostic indicators. These findings highlight the need for tailored surveillance and treatment strategies to improve outcomes in this unique patient population.