ESTRO 2022 - Abstract Book

S211

Abstract book

ESTRO 2022

requires an experienced team, the costs are relatively high, and the learning curve is slow. The aim of the present study is to evaluate the therapeutical effectiveness of linac-based stereotactic radiosurgery (SRS) in the treatment of malignant spasticity. Materials and Methods patients with spasticity to the lower limbs unresponsive to systemic therapies were treated with linac-based SRS to the spinal nerves responsible for the spasms within a prospective observational trial (n° 51262). Treatment dose was 45 Gy in a single fraction delivered with VMAT technique. The primary end-point was the reduction of the muscular resistance to passive movement measured with the Modified Ashworth Scale (MAS). Secondary end-points were toxicity, quality of life, and spinal nerves radiological features (fractional anisotropy, diffusivity). Results from December 2020, the first 4 patients were treated at our Institution. The first patient was treated at the bilateral nerves L4-S1 and had a complete spasms resolution the day after SRS administration that lasts 10 months after treatment. The second was treated at bilateral levels L3-L5 and had a progressive reduction up to 40% of the spasms over 4 months (fig. 1). The third patient was treated at the bilateral L4-5 and left S1. After 2 months, she had a MAS reduction (2 versus 3), however she died of thromboembolism 6 months after SRS. Patient 4 had MAS 3 and was treated at the bilateral L3-4. Few days after SRS administration he had a complete response to treatment with MAS 0, which lasted 3 months after treatment. No acute treatment-related toxicities or spasticity relapse were reported.

Figure 1. Treatment plan and DVH of patient 2

Conclusion the present is the first clinical report on the use of a linac-based SRS for the treatment of malignant spasticity. These preliminary results with a short follow-up documented a clinical activity of SRS that will be explored in a larger population to better assess effectiveness, toxicity, and duration of the response.

Award Lecture: E van der Schueren Award

SP-0252 Radiotherapy: Art or Science

P. Hoskin 1

1 Mount Vernon Cancer Centre and University of Manchester, Division of Cancer Sciences, Northwood and Manchester, United Kingdom Abstract Text Modern medicine is driven by scientific endeavour and radiotherapy is no exception. The practice of radiation oncology demands study in radiobiology, radiation physics and statistics, all hard data driven sciences leading to their own principles and laws which guide our use of radiation to cure and palliate cancer. Clinical practice demands high level clinical trial evidence to define our protocols and guidelines. Yet closer examination reveals that let loose in the clinical setting, faced with real patients the radiotherapist/radiation oncologist/clinical oncologist gives only passing heed to the latest science. Examples abound. There is a vast warehouse of data showing the efficacy of single doses of radiation in many palliative settings in particular metastatic bone pain yet when we survey practice on average only 30-40% of patients are treated with single doses. Training, reimbursement and prejudice (ie lack of understanding and belief) are the usual reasons put forward to explain this but perhaps a more generous view is that we all practice the art of medicine not the blind application of science. We recognise that real patients do not usually fit the guidelines, evidenced by the difficulty in accruing patients into clinical trials where the entry criteria are too rigid. We also know them as individuals with their own beliefs, sociological background and expectations to whom we apply our scientific knowledge. Plato says that art imitates the objects and events of ordinary life. Radiotherapy is moving into a new era; artificial intelligence and machine learning is rapidly evolving to replace many of the traditional tasks undertaken by the radiotherapist; computers will take over the drudge of volume definition, treatment planning, verification and delivery; protocol deviations according to individual whim will be highlighted and outlawed. Against this background what remains for the radiotherapist of the future?