Objective Bone metastasis is one of the common complications of breast cancer patients, which seriously affects the survival and prognosis of patients. The aim of this study is to investigate the expression and clinical significance of serum vitamin D-binding protein(VDBP), fibroblast growth factor 23(FGF23)and Klotho in breast cancer bone metastases.

Methods Ninety-five female breast cancer patients from our hospital from 2019-08-01 to 2021-08-01 were collected as the research subjects, the bone metastasis was diagnosed by imaging and histopathology, and the 95 patients were grouped into 36 cases with bone metastasis and 59 cases without bone metastasis. Analysis of clinicopathological features of patients in both groups; Patient peripheral blood samples were collected, the quantitative analysis of VDBP, FGF23 and Klotho in serum was carried out by ELISA; the correlation between the indicators was analyzed using the Spearman correlation coefficient; Logistic regression analyzed the influencing factors of bone metastasis in breast cancer patients; the value of serum VDBP, FGF23 and Klotho levels in predicting bone metastasis in breast cancer patients was analyzed by ROC curve.

Results There was a significant comparison of pathological grades in patients with bone metastasis and non-bone metastasis breast cancer(P < 0.05). The serum levels of VDBP, FGF23 and Klotho in patients with bone metastases and non-bone metastases were as follows: (80.35±29.34)and(115.18±48.69) ng/mL, (658.35 ± 201.19) and (405.36 ± 154.42) ng/mL, (155.82 ± 40.29) and (229.35 ± 72.46) ng/mL, and the differences were statistically significant between the two groups(P < 0.05). Spearman correlation analysis showed that VDBP in serum of breast cancer patients with bone metastases was correlated with the pathological grade of breast cancer (P < 0.05);the levels of FGF23 and Klotho were related to pathological grade, bone pain, visceral metastasis and metastasis site(P < 0.05). VDBP, FGF23 and Klotho levels were independent factors influencing the occurrence of bone metastasis in breast cancer(P < 0.05). The ROC curve results showed that the areas under the curve of VDBP, FGF23 and Klotho for predicting bone metastasis in breast cancer patients were: 0.733, 0.806, 0.761, and the best cut-off values were: 81.56 ng/mL, 573.501 pg/mL and 201.193 pg/mL. The area under the curve of the combined diagnosis of the three indicators was 0.820, which is higher than the area under the curve of the diagnosis of a single indicator.

Conclusions The serum levels of VDBP, FGF23 and Klotho can be used as reference indicators for bone metastasis of breast cancer, and have certain application prospects in the clinical diagnosis of bone metastasis of breast cancer.