Abstract
OBJECTIVES: The aim of this study was to compare the metastatic patterns of synchronous bone metastasis (SBM) and metachronous bone metastasis (MBM) in nasopharyngeal carcinoma (NPC). METHODS: This study included bone metastases in NPC patients from 2005 to 2016 in a Chinese hospital. Cohort 1 was collected from 2005 to 2010 for discovery, and Cohort 2 from 2011 to 2016 for validation. The chi-squared test, Wilcoxon rank sum test, and Kaplan-Meier technique were used to compare site, time, and survival between cohorts 1 and 2. Prognostic factors were analyzed using univariate or multivariate Cox regression. RESULTS: Cohort 1 had 112 individuals with SBM and 394 with MBM, and cohort 2 had 328 with SBM and 307 with MBM. The thoracic vertebra was the most frequently affected site of metastasis. Patients with SBM more often had metastasis to the cervical vertebrae compared with patients with MBM (34.5% vs. 22.3%, p < 0.05). Patients with SBM had better overall survival (42.2 months, 95% CI: 33.9-50.7) than patients with MBM (24.9 months, 95% CI: 22.2-28.7). Age at bone metastasis detection, metastasis to other organs, and more bone metastasis locations were associated with worse prognosis. The majority of MBMs occurred at 7 to 18 months after NPC diagnosis. CONCLUSION: Radiotherapy does not modify the metastatic patterns of NPC bone metastases. Patients with SBM tend to have metastasis to the cervical vertebra, which is close to the nasopharynx. Paying more attention to bone metastases during follow-up in the first 2 years after an NPC diagnosis.