The role of PET-CT in the evaluation of the response of the vertebra metastases in stereotactic radiosurgery

Abstract

Purpose: The aim of this study was to evaluate the role of positron emission tomography in assessing the response of stereotactic radiosurgery (SRS) for vertebral metastases(VM).

Materials and Methods: Patients who received 16 Gy or 18 Gy SRS with no history of vertebral compression fracture, proven histologies except small-cell lung carcinoma and hematologic malignancies which are known as radio sensitive tumors, available pre- and post SRS PET images were included. All vertebral segments were categorized according to spinal instability neoplastic score in terms of stability and PET Response Criteria in Solid Tumors (PERCIST) criteria was utilized for treatment response.

Results: Seventy-five patients with 119 VS (101 single, 9 double VS) received SRS. Breast cancer (66.7%) was the commonest pathology. Most patients (70.6%) had SINS 06.The local control was achieved in 87.4% VS with a 1-year local relapse -free survival rate of 92.5%. The median PET-CT time for the first SRS response assessment was 3-months (range:1-3.5 months) and there were only 4 (3.3%)local relapses in contrast to the positive responses in the remainders (30.3% complete, 43.7% partial responses and 22.7% stabil disease). While there were 11 local relapses in the last PET-CT response, no patient experienced any relapse complete response was achieved in the first PET-CT.Complete response in the first PET-CT was correlated with positive response in the last PET CT also.

Conclusion: First PET-CT response after SRS seems to be valuable in anticipation of both the final vertebral response status and planning of alternative interventions for non-responders.