ESTRO 38 Abstract book

S230 ESTRO 38

OC-0437 Update of moderate dose-escalation with perioperative HDR brachytherapy in soft tissue sarcomas X. Chen 1 , A. Montero 1 , J. De las Heras 2 , E. Sanchez 1 , O. Hernando 1 , M. Lopez 1 , J. Garcia 3 , M.A. De la Casa 3 , D. Zucca 3 , R. Ciervide 1 , M. Garcia-Aranda 1 , J. Valero 1 , R. Alonso 1 , J. Marti 3 , L. Alonso 3 , P. Garcia de Acilu 3 , P. Fernandez-Leton 3 , C. Rubio 1 1 University Hospitals HM Sanchinarro - Puerta del Sur, Radiation Oncology, Madrid, Spain; 2 University Hospitals HM Sanchinarro, Orthopaedic Surgery, Madrid, Spain ; 3 University Hospitals HM Sanchinarro - Puerta del Sur, Medical Physics, Madrid, Spain Purpose or Objective Conservative surgery in combination with local radiation therapy is considered a standard approach for soft tissue sarcomas (STS). A close relationship exists between total radiation dose and local control. We report our experience about the feasibility of perioperative brachytherapy (PoBT) with a moderate dose-escalation in the multidisciplinary management of soft tissue sarcoma. Material and Methods From May 2015 to October 2018, 22 patients (p), 13 men and 9 women, with a median age of 61.5 years (range 7 – 77 years) underwent perioperative brachytherapy (PoBT). Histology: 7 p (32%) liposarcoma, 5 p (23 %) fusocellular sarcoma, 3 p (14 %) desmoids tumor, 5 p (23 %) fibroblastic sarcoma,1 p (4%) pleomorphic sarcoma and 1 p (4%) malignant glomus tumour. Tumor location: thigh 14 p (63%), trunk 4 p (18%), arm 3 p (14%), neck 1p (4%).Tumor staging according to the AJCC 8th ed (2016): 5 p IA, 9 p IB, 5 p II, 2 p IIIA and 1 p IIIB. PoBT procedure was performed by using 6F plastic catheters placed on the surgical bed at the time of tumor excision. Sixteen (73%) patients obtained R0 resection and 5 p (23%) R1 resection. Plastic catheters were placed either parallel or perpendicular to the surgical incision at 1.5- 2 cm intervals to ensure adequate dosimetry. CT simulation with 1.5 mm slice thickness was done in the fourth or fifth day after surgery once the sewer system was retired. A total 16.5 Gy was delivered to the PTV in 3 fractions of 550 cGy in 20 p; 1 p received 4 fractions of 400 cGy and 1p received 3 fractions of 500 cGy. Fractions were separated at least 6 hours. Catheters were retired after the last fraction. Results All p received external beam radiotherapy (EBRT) before or after brachytherapy at a mean dose of 50 Gy in 25 fractions. Conformal 3D radiotherapy planning was used in 7 p (32%), intensity modulated radiotherapy (IMRT) in 10 p (45%) and volumetric modulated arc therapy (VMAT) in 4 p (18%). Six p (27%) underwent pre-operative radiotherapy whereas 16 p (73%) post-operative radiotherapy. One of the biological characteristics of sarcoma is their relatively low α-β ratio. Assuming an alpha/beta ratio of sarcoma cells as 4 our calculation of tumor BED is as following: (2Gy x 25fx) + (5.5Gy x 3fx) = 114.19Gy which corresponds to an accumulated EQD2Gy for tumor of 76.12Gy. With a median follow-up of 16 months (range 0.2 – 37.5 months), 1 p had developed marginal local relapse at 7.6 months of follow-up. In-field local control, distant-metastases free survival and overall survival are of 100%. No grade 3 or higher toxicity was observed. Conclusion Peri-operative brachytherapy is feasible and well tolerated and allows a moderate dose-escalation in patients with soft-tissue sarcomas.

1 University Hospital Zürich, Department of Radiation Oncology, Zurich, Switzerland Abstract text Radiation Oncology is unique as a field, where excellence in care and advances in research are only possible by closest collaboration of multiple professions: medical physics, nursing, radiation oncology, radiation technologists and radiobiology. The progress in our field is documented by significantly and clinically relevant improved outcome over time and this has been achieved in all frequent cancer sites of lung cancer, prostate cancer, breast cancer, rectal cancer and many small cancer sites. Medical physics has been a key driver of these advances and has strongly contributed to reshape the way radiation oncology is practiced and perceived today: clinically effective, well tolerated and cost- effective. Both innovation AND translation are responsible for these success stories. Intensity-modulated radiotherapy, image-guidance and stereotactic-body radiotherapy are just some exemplary innovations which all improve outcome of our today’s cancer patients: these advances have been (co-)developed by Medical Physics, jointly implemented by all professions, successfully evaluated in clinical trials, incorporated into international and multidisciplinary guidelines and are today standards of care in our societies. All innovations can be summarized under the umbrella of precision medicine: to adapt radiation oncology to the patient-individual disease aiming to deliver the right treatment to the right patient and the right time. Consequently, radiation oncology has practiced precision medicine long before this “buzz-word” was adopted in medicine and oncology. This is a huge opportunity for radiation oncology in general and medical physics in particular: to be at the forefront of current research and clinical advances in oncology and medicine. Precision medicine is fundamentally based on individual patient and disease characterization: digitalization, standardization, collection, analysis and interpretation of various patient and disease characteristics within multi- level prognostic and predictive models has already been established in radiation oncology. More comprehensive patient and disease characterization beyond currently available biomarkers has been pioneered by Medical Physics using e.g. quantitative image analysis – Radiomics. Artificial intelligence and machine learning will be mandatory for handling and interpretation of these massive data and are already today routine in radiation oncology. Medical physics has therefore a lot to offer to the progress of precision medicine in general, not only in the field of radiation oncology and also not restricted to oncology. It will be critical to distribute and balance the limited resources between these different fields of research, between “traditional” radiation oncology medical physics and “beyond borders” radiation oncology. This will strengthen Medical Physics. However, if Radiation Oncology overall is open for these developments, our discipline and finally our cancer patients will benefit from continuing our multi-professional nature.

Award Lecture: Honorary Physicist Award Lecture

SP-0438 Precision medicine – an opportunity for medical physics and radiation oncology M. Guckenberger 1