ESTRO 36 Abstract Book

S45 ESTRO 36 2017 _______________________________________________________________________________________________

compression of irradiation. Pain relief meant the achievement of the score 3 down in the scale. Results The overall degree of response to radiotherapy was 51/62 (82.2%). The bone densities of both IMB and INMB dropped by about 10 % from immediate to one month after radiotherapy. The bone densities of IMB lesions increased after then. There are close relations between the pain control effects of radiotherapy and bone mineral density change. Overall, from 3 months onward, the bone densities of effective patients were significantly higher than its pre-radiotherapy value. Conclusion Radiotherapy provide a meaningful supportive but not perfect prolong benefit to many patients with bone metastases. Mineralization effects of radiation therapy depend on the characteristic metastases, especially the effect of radiotherapy. PV-0090 The risk of myelopathy after reirradiation of the spinal cord. M. Hiul Suppli 1 , P. Munck af Rosenchold 1 , H. Pappot 1 , S.A. Engelholm 1 1 Rigshospitalet, Department of Oncology, Copenhagen, Denmark Purpose or Objective Spinal re-irradiation has for a long time been considered unacceptable due to the risk of radiation induced myelopathy (RIM). Previous studies of of reirradation have demonstrated the possibility of gait preservation with minimal risk of RIM. Recommendations regarding treatment dose, cumulative dose and time between treatments to estimate the risk of RIM based on previously reported data exist. However, these recommendations have been based on retrospective analysis of smaller cohorts of patients. Very limited data on the risk of vertebral fractures (VF) is presently available for fractionated palliative radiotherapy. In this study we investigate the risk of RIM and VF in a large cohort of consecutive patients treated multiple times with palliative radiotherapy of the spine. Material and Methods From the year 2010 until 2014 a total of 2387 patients received spinal irradiation with a palliative intent for metastatic spinal cord compression. All patients were reviewed for prior irradiation at either our facility or another radiotherapy department. We find that 249 patients had potentially overlapping fields on the spinal cord. After analysis of treatment plans, we find that 220 patients received re-irradiation of the spinal cord. Clinical and treatment data was obtained from the patients’ records and RT planning system. Follow-up data was obtained with approval from the Danish board of health. Results Patients had metastatic disease from breast, prostate, lung, haematological or other cancers (22.7%, 21.8%, 21.4%, 3.2% and 30.9% respectively). Median time from 1st irradiation until 2nd irradiation was 306 days, range 15 days-33 years. Median number of days from 2nd irradiation until death was 91 days (range 1 days-5 years). Median cumulative dose was 57.8 Gy (EQD2, with α/β=2)), range: 20.0-93.0Gy. Myelopathy or vertebral fracture likely related to re-irradiation was observed in fifteen patients. One patient developed myelopathy, for an additional five patients, myelopathy could not be ruled out from retrospective observations. Nine patients experienced a vertebral fracture within the treatment field, which resulted in neurological deficit for eight of these patients.

Conclusion Patients suffering from spinal metastases and impending spinal cord compression are often treated with radiation. Patients with neurological deterioration due to metastatic progression within a previously treated site of the spinal cord face the risk of either fulminant metastatic spinal cord compression or toxicity due to re-irradiation. Within our cohort the incidence of myelopathy remained low, but vertebral fractures were more prevalent. Patients with spinal metastases treated with repeated radiotherapy and potential long term survival should be considered for spinal instrumentation.

PV-0091 Quantifying the Gap Between Radiotherapy in the Elderly and the Demand for Age-Agnostic Treatment. T. Mee 1 , N.F. Kirkby 1 , K.J. Kirkby 1 , R. Jena 2 , A. Choudhury 3 1 University of Manchester, Division of Molecular & Clinical Cancer Sciences, Manchester, United Kingdom 2 University of Cambridge, Department of Oncology, Cambridge, United Kingdom 3 The Christie NHS Foundation Trust, Clinical Oncology, Manchester, United Kingdom Purpose or Objective Radiotherapy is prescribed less in the elderly compared to other age cohorts. However, current research suggests that there is little clinical evidence for this. In England, the demand for radiotherapy services is greater than capacity, so any increase in demand must be considered carefully. This can be done using population-based modelling systems. The potential effects of changing the prescription paradigm in the elderly needs to be modelled for a health care system at a local level to estimate the impact on demand for services, due to variations in local demographics and incidence rates. Material and Methods The Malthus model, an evidence-based tool for modelling radiotherapy demand, was used to calculate the demand for radiotherapy, broken down into age groups, for the whole of England for 2015. The simulation was completed in an age-agnostic manner. The simulation outputs were compared to the Radiotherapy Data Set, a dataset of delivered radiotherapy within the National Health Service