Bone metastases are a frequent event in patients with solid tumours. Although great advances have been made in the treatment of these patients, the identification of new, accurate indicators of bone response would greatly facilitate the clinical management of the disease. The RANK/RANKL/OPG pathway is significantly involved in bone metastasis formation. The main aim of our study was to evaluate the role of circulating RANK, RANKL and OPG levels in predicting bone response. Marker accuracy was also compared with that of the conventional tumour marker NTX. We performed a prospective study on 49 patients with bone metastases from breast, lung and prostate cancer undergoing treatment with ZA. Patients were monitored for one year with blood tests, clinical evaluation, and instrumental exams according to MD Anderson response evaluation criteria and PERCIST. Circulating RANK/RANKL/OPG transcripts and NTX levels were evaluated by Real Time PCR and immune enzymatic assay, respectively. Baseline RANKL levels differed significantly between responders and non responders, whereas no differences in NTX levels were observed in either group. ROC curve evaluation for all markers revealed that RANKL was the most accurate, with an AUC of 0.74 (95%CI 0.54-0.93). RANKL, target of the novel monoclonal antibody Denosumab, was the most accurate predictor of bone response in our series of patients with bone metastases. Its use could potentially improve clinical practice as current bone response evaluation is still somewhat problematic.
Disclosure: The authors declared no competing interests.