Radt-24. a prospective trial evaluating the efficacy of reirradiation to bony metastases with stereotactic body radiation therapy

Abstract INTRODUCTION Bone metastasis is common in advanced-stage cancer patients. While reirradiation of metastatic tumors offers significant symptom control, major limits exist on the possible dose delivered to previously irradiated disease sites. Stereotactic body radiation therapy (SBRT) offers the potential to avoid delivering toxic radiation doses to the spinal cord and other organs at risk by delivering large doses with steep dose gradients. METHODS We developed a prospective study including 44 patients with recurrent bone metastasis that were treated to assess the effectiveness of SBRT on local control at or before 6 months as a primary endpoint and local progression-free survival (LPFS), Progression-free survival (PFS), and overall survival (OS) as a secondary objective. RESULTS Patients median age was 62.5 years (22.7% female and 77.3% male). The majority of patients received reirradiation to a spinal lesion (29/44, 65.9%) of various primary disease sites predominantly prostate (13/44, 29.5%), lung (8/44, 18.2%), and renal cell (5/44, 11.4%). The most common dose prescriptions were 30 Gy in 5 fractions (24/44, 54.5%). Of the participants, 41 (93.2%) experienced local control at or before 6 months, with 3.6 median months to local progression for those who progressed. 48% and 36.5% of the cohort maintained LPFS at 2 years, and 3 years respectively with a local progression-free rate of 89.5% at 2 and 3 years. OS was maintained in 50.9% and 38.8% of patients at 2 years and 3 years respectively. CONCLUSION SBRT offers an effective and less toxic approach for the reirradiation of recurrent metastatic tumors as it can prevent associated toxicities to the surrounding normal tissues and maintain a local progression-free rate in a large percentage of patients. We believe that more clinicians should offer SBRT as an effective option for recurrent metastatic bone tumors especially involving the spinal vertebrae.