ESTRO 38 Abstract book

S878 ESTRO 38

the difference in HU between the reference vertebra and the lesion was 172.5 HU (95% CI: 110.1 - 234.7; P < 0.001). An example of the change in bone density in the ROI before and after radiotherapy can be seen in figure 1. At 3 months, the difference between the reference vertebrae and the lesion decreased to 61.6 (95% CI: -15.3 – 138.4, p=0.178). Taking all first follow-up scans into account, the mean difference in HU in the metastatic lesions between baseline and first follow-up was 39.1 HU (95% CI: -25.5 – 103.7; P = 0.228). For all first-follow-up scans, the mean difference between the reference value and the lesions declined to 108.3 HU (95% CI: 15.7-200.9, p=0.057). When patients used bisphosphonates during the RT, an increased difference in HU was measured compared to patients who were not using bisphosphonates(192.8 vs 53.8HU, p=0.008).

Acute toxicity was documented in only one patient with colitis G2, late toxicity was not reported. One-, two- and three-year overall survival was 65.7%, 65.7% and 56%, respectively.

Conclusion SART is a feasible treatment for non-spinal bone metastasis which provides good local control and excellent pain control, decreasing time of machine usage without additional toxicity. Both longer follow-up and increased number of patients are necessary to adequately evaluate actual significance of these clinical outcomes. EP-1629 Recalcification in lytic bone metastases of the spine after radiotherapy B. Pielkenrood 1 , T. Visser 1 , W. Foppen 2 , J. Van der Velden 1 , W. Eppinga 1 , N. Kasperts 1 , G. Bol 1 , L. Verkooijen 1 , J. Verlaan 3 1 UMC Utrecht, Radiotherapy, Utrecht, The Netherlands ; 2 UMC Utrecht, Radiology, Utrecht, The Netherlands ; 3 UMC Utrecht, Orthopedic Surgery, Utrecht, The Netherlands Purpose or Objective Due to an increased survival of cancer patients, the incidence of bone metastases has increased. Osteolytic bone metastases may cause fracture, pain, instability, and spinal cord compression. It has been reported that radiotherapy (RT) may induce recalcification in these lesions. It is not completely clear, however, which factors are associated with recalcification. The aim of this study was to investigate the change in bone mineral density in spinal metastases after RT. Material and Methods Within the UMC Utrecht PRESENT cohort we identified all patients who received radiotherapy for lytic spinal metastases. Patients were included if CT-scan was available pre- and post-RT. Bone density of the metastases was measured in Hounsfield units (HU). A preset region of interest (ROI) was drawn manually in each metastatic lesion. As a reference, a measurement of bone density in vertebrae without a lesion that did not receive RT was used. Factors tested for association were origin of the primary tumor, RT dose and scheme, and use of bisphosphonates. Change in bone density was analyzed using the paired T-test, differences between the treated lesions and the reference value was analyzed using the Welch T-test. Factors associated with the recalcification were tested with linear regression analysis. Results A total of 119 patients with a lytic spinal metastasis were identified. Because of unsuitable or missing baseline or follow-up scan, osteosynthesis material in the ROI or a fracture in the ROI, 86 patients were excluded. In 33 patients, 51 lesions were identified. The median age at baseline was 60 years (IQR: 54-64), and the median follow up was 8.2 months (IQR: 3.2 – 17.8). Of the available follow-up scans within 3 months (n=21), the difference between baseline and follow-up in the metastatic lesions was 103.0 HU (95% CI: 55.1 - 150.8; p < 0.001). At baseline,

Conclusion In this confined study of 33 patients with lytic spinal metastases, we found that recalcification could be induced by radiotherapy. To confirm the effect of radiotherapy and other factors, a study with an increased sample size should be considered. EP-1630 A Multidisciplinary approach to Palliation - Rapid Access Targeted Personalised Radiotherapy Clinic A. Sharif 1 , R. Mamon 2 , K. Gaunt 3 , N. McAndrew 4 1 GCUK, Medical Physics, Nottingham, United Kingdom ; 2 GCUK, Medical Physics, Milton Keynes, United Kingdom ; 3 GCUK, Service of the Future, London, United Kingdom ; 4 GCUK, Medical Physics, London, United Kingdom Purpose or Objective To offer Palliative VMAT Radiotherapy as a standard care within a distributed network of centres to all eligible Palliative Patients within 24 hours of referral to treatment commencement (Rapid Access). Providing patients access to more personalised and targeted radiotherapy results in fewer side effects, reduced time in a hospital bed and reduced reliance on expensive drugs. Material and Methods A mutlidisciplinary project group set up to map patient pathway and agreed pre- requisites to support delivery of the service. Efficiencies in the planning and checking processes were made using Protocol based automation and automated Phantomless plan QA. The planning and checking is completed by a distributed Medical Physics team using a Departure board to prioritise urgency of tasks. On Clinic days the palliative patients would be a priority .