Response Assessment After Stereotactic Body Radiation Therapy for Spine and Non-spine Bone Metastases: Results From a Single Institutional Study

Abstract

Background The use of stereotactic body radiation therapy (SBRT) for tumor- and pain control in patients with bone metastases is increasing. Here, we report response assessment after bone SBRT using radiological changes through time and clinical examination of patients. MethodsWe analyzed retrospectively the oligo-metastatic/progressive patients with bony lesions treated with SBRT between 12/2008 and 10/2018 in our institution. Radiological data were obtained from imaging modalities used for SBRT planning and follow-up (FU) purposes in PACS and assessed by two independent radiologists blind to the time of treatment. Several radiological changes were described. Radiographic response assessment was classified according to University of Texas MD Anderson Cancer Center criteria. Pain response was captured pre- and >= 6 months post-SBRT.ResultsA total of 35 of the 74 reviewed patients were eligible, presenting 43 bone metastases, with 51.2% (n=22) located in vertebral column. Median age at the time of SBRT was 66 years (range, 38-84), and 77.1% (n=27) were male. Histology was mainly prostate (51.4%, n=18) and breast cancer (14.3%, n=5). Median total radiation dose delivered was 24 Gy (range: 24-42), in three fractions (range: 2-7), prescribed to 70 - 90% isodose-line. After a median FU of 1.8 years (range, 0.1-8.2) for survivors, complete-/ partial response, stable (SD), and progressive disease occurred in 0%, 11.4% (n=4), 68.6% (n=24) and 20.0% (n=7) of the patients respectively. Twenty patients (57.1%) died during the FU time, all from disease progression, yet 70% (n=14) from this population with local SD after SBRT. From patients who were symptomatic and available for FU, almost 50% reported pain reduction after SBRT.ConclusionsEighty percent of the patients showed local control (LC) after SBRT for bone metastases. Pain response was favorable. For more accurate response assessment, comparing current imaging modalities with advanced imaging techniques such as functional MRI and PET-CT is warranted.Trial registrationRetrospectively registered.