BACKGROUND: Metastatic bone disease is a frequent complication of advanced non-small-cell lung cancer and causes skeletal-related events which result in a poor prognosis. A standard method to assess the therapeutic response of bone metastases does not currently exist. We used dynamic contrast-enhanced MRI to obtain quantitative measures to assess the suitability of this technique to gauge therapeutic response to vinorelbine-cisplatin plus rh-endostatinfor previously untreated non-small cell lung cancer with bone metastases. METHODS: We did a phase 4, randomised, prospective, double-blind, placebo-controlled clinical trial in Shanghai Sixth People's Hospital, Shanghai, China. Inclusion criteria were non-small-cell lung cancer patients with bone metastases confirmed by pathology or cytology; available imaging data of pelvic metastatic lesions; aged 18 to 75 years old; expected survival at least 3 months; not receiving taxane, bevacizumab, thalidomide, rh-endostatin, or bisphosphonate; not having radiation therapy within 3 months of enrollment into study; normal results of routine blood tests, liver and kidney function, and electrocardiogram; absence of cardiovascular disease, autoimmune disease, vasculitis, severe infection, diabetes, and other concomitant disease; and signed informed consent. Exclusion criteria were receiving granulocyte colony stimulating factor or granulocyte-macrophage colony stimulating factor during chemotherapy, intolerance to adverse reaction, and allergy to contrast agents. Patients were randomly assigned to treatment group and control group at a ratio of 2:1 by random code generation by an independent biostatistician in a double-blind fashion. Participants received either vinorelbine-cisplatin plus rh-endostatin or vinorelbine-cisplatin plus placebo. Vinorelbine (25 mg/m2) and cisplatin (75 mg/m2) were administered intravenously on the first day of a 21 day cycle. Patients received rh-endostatin (7·5 mg/m2) or placebo on days 1-14 of a cycle. The primary end points were objective response rate (complete remission+partial remission)/total × 100) and disease control rate (complete remission+partial remission+stable disease)/total × 100). Measurements including Ktrans, Kep, and Ve were evaluated by dynamic contrast-enhanced MRI before treatment and after completion of 2 treatment cycles. Blood concentrations of bone metabolites, tumour markers, and tumour vascular growth related factors were measured before and after treatment. Comparisons were made using paired t-test. Kaplan-Meier survival analysis was used to indicate the correlation between some measurements and progression-free survival or overall survival. The difference in Ktrans between patients who had partial remission or stable disease group and those who had disease progression was tested using the Chi-square test. All statistical analyses were performed with SPSS version 21.0. This trial was approved by the State Food and Drug Administration (No: S20050088) and China State Food and Drug Administration. The trial is registered with China Clinical Trials Registry, number chictr-ctr-09000569. Written informed consent and ethical approval was obtained. FINDINGS: We enrolled 33 patients (aged 52-70, 15 men and 18 women) of whom 28 were evaluable (20 in treatment group and 8 in control group). Five patients were excluded: 2 patients in treatment group and 1 patient in control group used granulocyte-macrophage colony stimulating factor, and 2 patients in the control group refused treatment. Objective response rate was higher (30% vs 0%; p<0·00001), mean overall survival was longer (21·44 [SD 17·28] vs 7·71 [4·68] months, p=0·008), and reduction in capillary permeability (measured by Ktrans) was greater (60·0% vs 4·4%; p=0·026) in the group given rh-endostatin than in the control group. Disease control rate was 80% in the treatment group and 75% in the control group (p=0·07). Overall survival was longer in patients with a greater than 50% reduction in Ktrans than in patients with a decrease of up to 50% (13·2 [1·8] vs 9·8 [0·2] months, p=0·026). INTERPRETATION: Addition of rh-endostatin to treatment with vinorelbine-cisplatin increased the treatment response in patients with non-small cell lung cancer and bone metastases. Quantitative analysis using dynamic contrast-enhanced MRI can be used to evaluate therapeutic response and to predict survival of bone metastases after anti-angiogenesis therapy. Limitations of this study include the small number of patients and the single-centre design. FUNDING: National Natural Science Foundation of China [grant number 81201628].