The spine instability neoplastic score (SINS) in the assessment of response to radiotherapy for bone metastases

Background: Vertebral metastases are often causing pain and spine instability. Radiotherapy is of significant benefit for painful spine metastases but the response can be very variable. The spine instability neoplastic score (SINS) is a recent classification system for diagnosis of spinal instability caused by vertebral metastases. We analysed the degree of pain relief, the need of drug therapy and the imaging features and the SINS before and after radiotherapy. In particular, we investigated the possible correlation of spine instability defined by pre-treatment SINS with pretreatment pain and with response to radiotherapy. Material/methods: This study included 121 patients with spine metastases treated with palliative 3D conformal radiotherapy. Pain “at rest” and “breakthrough pain”, need for drug therapy in terms of “anti-inflammatory”, “weak opioid”, “strong opioid”, imaging studies and SINS were assessed before and after radiotherapy. Statistical analysis was performed by the correlation coefficient of Spearman and Kruskal–Wallis test. Results: Pain relief after radiotherapy was observed in 50.4 and 57.8% of patients in terms of pain at rest and breakthrough pain, respectively. The correlation between pain before radiotherapy and SINS was not statistically significant for both pain at rest (p = 0.4) and breakthrough pain (p = 0.49). The correlation between pain response after radiotherapy and SINS was statistically significant for both pain at rest (p = 0.007) and breakthrough pain (p = 0.047). Discussion/conclusion: The degree of instability, classified according to SINS, resulted to be predictive factor for pain response after radiotherapy. SINS might become a valid tool to identify those patients who can benefit the most from radiotherapy.