Subdivision of Nasopharyngeal Carcinoma Patients with Bone-Only Metastasis at Diagnosis for Prediction of Survival and Treatment Guidance

The purpose of this study was to subdivide M1 stage nasopharyngeal carcinoma (NPC) patients with bone-only metastases for prognosis prediction while identifying the treatment effect of locoregional radiotherapy (LRRT) and metastasis radiotherapy (MRT) among patients with different risk. From November 2006 to October 2016, a total of 226 patients with bone-only metastasic NPC were retrospectively enrolled. All patients developed distant lesions before receiving treatment. All potential prognostic factors were considered and the correlation of the M1 subdivisions with overall survival (OS) was determined by Cox regression hazards model. Kaplan-Meier curves were used to appraise survival condition and log-rank testing was used to compare the differences. The median follow-up time was 33.9 months (range, 3 to 126 months). According to multivariate Cox proportional hazard analysis, the number of metastatic lesions and Epstein-Barr virus (EBV) DNA status after palliative chemotherapy (PCT) were independent prognostic factors for OS. Thus, we subdivided patients into three risk groups according to these two factors. Systemic chemotherapy combined with LRRT may benefit patients in low- and intermediate-risk groups but not in the high-risk group. Further aggressive MRT based on systemic chemotherapy showed no survival benefit in any risk group. The stratification of NPC patients with bone-only metastasis based on EBV DNA after PCT and the number of metastatic lesions provided promising prognostic value and could aid clinicians in person-specific treatment.