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. We report response assessment after bone SBRT using radiological changes through time and clinical examination of patients. Methods We analyzed retrospectively oligo-metastatic/progressive patients with bony lesions treated with SBRT between 12/2008 and 10/2018, without in-field re-irradiation, in our institution. Radiological data were obtained from imaging modalities used for SBRT planning and follow-up purposes in picture archiving and communication system 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 and the neurological deficit were captured before and at least 6 months after SBRT. Results A total of 35 of the 74 reviewed patients were eligible, presenting 43 bone metastases, with 51.2% (n = 22) located in the 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 follow-up of 1.8 years (range < 1–8.2) for survivors, complete or partial response, stable, 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 follow-up time, all from disease progression, yet 70% (n = 14) from this population with local stable disease after SBRT. From patients who were symptomatic and available for follow-up, almost half (44.4%) reported pain reduction after SBRT. Conclusions Eighty percent of the patients showed local control 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, in a prospective and standardized way is warranted. Trial registration Retrospectively registered.

Percutaneous CT-Guided Microwave Ablation Combined with Pedicle Screw Fixation Followed by Vertebroplasty (MASFVA): Initial Experience of a Minimally Invasive Treatment of Vertebral Metastases with Extension to the Vertebral Pedicle

“…Open surgical treatment, which consists of decompressive laminectomy with longlevel screw fixation and bone fusion, is indicated in cases of obvious spinal instability, clinically significant neural compression secondary to retropulsed posterior somatic wall or spinal deformity, intractable pain unresponsive to nonsurgical measures, and radiotherapy failure, but it is often of limited benefit in the management of spinal metastases due to its morbidity [2]. Some histological forms of bone metastases, such as those arising from sarcoma, renal cell carcinoma, non-small cell lung carcinoma, and melanoma, respond less well to radiotherapy [16]. Furthermore, the use of radiotherapy is limited by spinal cord cumulative dose tolerance [17].…”

State-of-the-Art Imaging Techniques in Metastatic Spinal Cord Compression

“…A common pitfall in post SBRT imaging is the phenomenon of pseudoprogression. This occurs when there is a significant increase in post-treatment lesion volume usually without significant clinical symptoms, with eventual stabilization or regression on subsequent imaging [117,151]. This is well documented in the brain, lung and liver [117].…”

“…However, more research may be needed as a recent case report demonstrated a patient with pseudoprogression in the form of an epidural mass [156]. The timeframe is also important, with pseudoprogression occurring within a few weeks up to 6 months post SBRT, in contrast to the late presentation of radio-necrosis which may occur years after therapy [151]. Growth confined within the 80% prescription isodose-line and lytic lesions (as opposed to sclerotic lesions) have also been shown to be predictive of pseudoprogression [155,157].…”

“…VCF is a commonly encountered complication of SBRT [151]. The incidence rate of VCF ranges from 11-39%, with a systematic literature review by Faruqi et al (2018) reporting a crude rate of 13.9% [158][159][160].…”

The Role of Post-Operative Radiotherapy for Non-Spine Bone Metastases (NSBMs)

“…The only major difference is that review studies have found that patients receiving single-fraction treatment have a higher incidence of requiring re-irradiation [ 11 ]. The efficacy of radiation in achieving pain control has also been found to hold true with the utilization of SBRT [ 41 ].…”