Positive effect of high RKIP expression on reduced distant metastasis by chemotherapy when combined with radiotherapy in locoregionally advanced nasopharyngeal carcinoma: a prospective study

The purpose of this prospective study is to investigate the predictive and prognostic significance of the Raf kinase inhibitory protein (RKIP) in locoregionally advanced nasopharyngeal carcinoma (NPC). Immunohistochemical assays were performed to detect the RKIP protein expression of samples from 212 patients with locoregionally advanced NPC. All patients were assigned randomly into the inductive chemotherapy plus radiation therapy (IC + RT) group, the concurrent chemoradiotherapy (CCRT) group, the inductive chemotherapy plus concurrent chemoradiotherapy (IC + CCRT) group, and the radiation therapy alone (RT) group. The patients in the IC + RT group were treated with IC using 2–3 cycles of cisplatin (80 mg/m²) and fluorouracil (500 mg/m²), repeated every 3 weeks, followed by radiotherapy. Those in the CCRT group were treated with weekly cisplatin (40 mg/m²) for 6–7 cycles during radiotherapy. In the IC + CCRT group, the chemotherapy prior to radiation was similar to the cisplatin–fluorouracil regimen in the IC + RT group, whereas it cisplatin regimen was identical to that in the CCRT group. The results show that RKIP is an independent prognostic factor for 5-year distant metastasis–free survival (DMFS), overall survival (OS), and progression-free survival (PFS). Patients with high RKIP expression benefited more from reduced metastasis in the IC + RT and the IC + CCRT group, with improved OS and PFS in each treatment group compared with that among patients with low RKIP expression. In the high RKIP expression subgroup, chemotherapy combined with radiotherapy improved the DMFS when compared with the RT group, but this effect was not observed in the low RKIP expression subgroup. RKIP was predictive of distant metastasis with good sensitivity and specificity. Clinically, high RKIP expression inhibited distant metastasis in advanced NPC, and its detection might be used to predict distant metastasis with good sensitivity and specificity. The effect of chemotherapy on distant metastasis in combined chemoradiotherapy might be related to the RKIP expression level. Patients with high RKIP expression showed more improved OS and PFS than their low RKIP expression counterparts. Higher RKIP expression improves the DMFS of patients who receive inductive high-dose cisplatin-based chemoradiotherapy, with or without concurrent cisplatin. Low RKIP expression is also a predictive marker for cancer progression and metastasis, which could be used to stratify patients with high risk of metastasis and death.