Serum alkaline phosphatase predicts survival outcomes in patients with skeletal metastatic nasopharyngeal carcinoma

OBJECTIVE Bone metastasis is frequently associated with nasopharyngeal carcinoma. The diagnosis and follow-up of bone metastatic patients usually relies on skeletal X-ray and bone scintigraphy, which are time-consuming and costly. This study aimed to evaluate whether serum alkaline phosphatase offers clinical value in predicting the clinical response and survival outcome for skeletal metastatic nasopharyngeal carcinoma. METHODS Serum alkaline phosphatase was measured at baseline and then before each cycle of treatment in 416 nasopharyngeal carcinoma patients with bone metastasis. The correlations between the pre-treatment and post-treatment alkaline phosphatase levels and the treatment efficacy were analyzed using the chi-square test. Survival was analyzed using the Kaplan-Meier method and then compared using the log-rank test. RESULTS Patients with elevated pre-treatment alkaline phosphatase (>110 IU/L) had significantly worse progression-free survival (P<0.001) and overall survival (P<0.001) than those with a normal level of this marker (≤110 IU/L). Patients with elevated post-treatment alkaline phosphatase had worse progression-free survival (P<0.001) and overall survival (P<0.001) compared with those with a normal level. Patients with normal pre-treatment and post-treatment alkaline phosphatase showed the most favorable prognosis. The Cox multivariate analysis revealed that only the pre-treatment and post-treatment alkaline phosphatase levels were independent prognostic factors for progression-free survival (HR ϝ 1.656, P<0.001; HR ϝ 2.226, P<0.001) and for overall survival (HR ϝ 1.794, P<0.001; HR ϝ 2.657, P<0.001). CONCLUSIONS Serum alkaline phosphatase appears to be a significant independent prognostic index in patients with skeletal metastatic nasopharyngeal carcinoma, which could reflect the short-term treatment response of palliative chemotherapy and the long-term survival outcomes.