Abstract Book

S917

ESTRO 37

During the observation period, 7.5% of patients noted a deterioration of the contracture or the topical condition, in 35% stagnancy was observed, and 57.5% of patients showed a reduction of the contracture and an improvement in the topical condition. After the RT, 87.5% of patients had no side effects, in 7.5% there was a slight skin erythema, 2.5% had superficial epidermis exfoliation, and 2.5% reported dry skin Conclusion The obtained results allow one to conclude that palmar fascia irradiation is an effective method of treatment for patients with Dupuytren's disease and it is characterised by a low proportion of complications. EP-1710 Pre- versus post-operative radiotherapy: complications after combined therapy for spinal metastases. B. Pielkenrood 1 , L. Pogoda 1 , J. Van der Velden 1 , H. Verkooijen 2 , J. Verlaan 3 , N. Kasperts 1 1 UMC Utrecht, Radiotherapy, Utrecht, The Netherlands 2 UMC Utrecht, Epidemiology, Utrecht, The Netherlands 3 UMC Utrecht, Orthopeadics, Utrecht, The Netherlands Purpose or Objective The majority of cancer patients develop bone metastases with the spine as most common location (30-70%). These metastases can cause pain, spinal instability, and spinal cord compression, thereby decreasing quality of life. To improve quality of life and preserve spinal stability, a combined treatment of surgical stabilization and radiation therapy (RT) is necessary for patients with spinal instability, furthermore mechanical pain will not improve after radiotherapy alone . Currently it is unknown whether pre- or postoperative RT is better. Therefore, we studied the rate of complications in patients who received pre-operative RT compared to patients who received post-operative RT. Material and Methods All patients receiving surgical therapy in combination with RT for spinal metastases between 2009 and 2017 where included in this study. Patients were identified from the PRESENT cohort, a prospective cohort of all patients treated with RT for bone metastases at the UMC Utrecht, and the spinal metastases database of the UMC Utrecht. Complications were defined as complications according to the Clavien-Dindo classification grade 2-4 or neurological damage without therapeutic options within 3 months after completion of treatment. Statistical analysis was done using IBM SPSS 23. Results Of the 142 patients receiving RT and surgery , 91 patients (64%) received pre-operative radiotherapy and 51 patients (36%) received post-operative radiotherapy. The number of days between radiotherapy and operation was 0-280 in the pre-operative RT group and 8-69 days in the post-operative RT group. Of all patients, 71 (50%) had any complication after the combined treatment. Most complications were in the post-operative RT group (53% vs. 45%). The rate of total complications between pre-operative and post-operative RT was not statistically different. (OR=0.74; 95% CI 0.35- 1.55)Most common complications were neurologic complications (n=27), and wound complications (n=10) . In the pre-operative RT group, 3 patients (6%) had wound complications. In the post-operative RT group, 7 patients (8%) experienced wound complications. In the pre- operative RT group, 12 patients(24%) had a neurological complications compared to 13 patients(14%) in the post- operative RT group. Neither the rate of wound

complications or neurological complications were statistically different in the pre-operative RT group vs. post-operative RT group(OR=0.75; 95% CI 0.12-3.48 for wound complications) and (OR= 1.56; 95% CI 0.60-3.96 for neurological complications) Conclusion These preliminary results show no significant differences in complication rates between patients who received pre- operative or post-operative RT for spinal metastases. In further research we can focus on the prevalence of complications within certain time frames pre- and postoperatively. EP-1711 Stereotactic body radiotherapy for oligometastatic bone metastases: a two-year follow-up study I. Guix 1 , A. Navarro 1 , A. Lozano 1 , M. Laplana 1 , J. Mases 1 , J. Gonzalez 1 , S. Almendros 1 , N. Garcia 1 , M. Stefanovic 1 , F. Guedea 1 1 Catalan Institute of Oncology, Radiation Oncology, Barcelona, Spain Purpose or Objective To evaluate the outcome of patients treated with stereotactic body radiotherapy (SBRT) for oligometastatic bone disease, in terms of distant progression-free survival (DPFS) and overall survival (OS). Secondary objectives were to appraise toxicity and pain control rates. Material and Methods From September 2012 to September 2017, 50 patients with 62 bone oligometastases were treated using SBRT technique at our center. Median follow-up time was two- years. Response to radiotherapy was analyzed according to RECIST criteria v1.1 and PERCIST criteria. All patients underwent MRI and PETCT scan alternatively, every 6 months, during that period. Pain flare was defined as an increasing of two points in the pre-treatment pain score. Toxicity was registered and graded according to Common Terminology Criteria for Adverse Events (CTCAE) v4.0. The survival analysis was performed using the Kaplan- Meier method. Results Median age was 57.13 years (r: 36-81). Primary tumors were: breast (45%), prostate (19%), lung (14’5%), kidney (6’5%), colon (3’2%) and others (11’8%). Out of the 62 bone metastases, 38 (61,3%) were located in the spine and the outstanding 24 (38,7%) in non-spinal bony locations. SBRT fractionation schemes were 16 Gy in a single fraction for spinal lesions and 22.5 Gy delivered in 3 fractions for flat and long bone metastases. With a median follow-up time of 23’77 months (r: 1-65), local control of the irradiated bone metastases was achieved in 83% of the cases. The two-year overall survival (OS) and distant progression-free survival (DPFS) were 73’5% and 45%, respectively. Median distant progression-free survival averaged 13’3 months (95% CI: 8’9-17’6), and median survival time was 43 months (95% CI: 26’9-59’1). Local response of the irradiated bone metastases was a prognostic factor regarding OS and DPFS. Seventy percent (35) of the patients with complete response at the oligometastatic site/s do not present systemic progression after 2 years of follow-up; whereas 80% (8) and 87’5% (7) of the patients with local progression or partial response of the irradiated bone metastases distantly progressed, respectively. Eighteen percent of patients had pain flare during or after the treatment. Only two patients (3’2%) experienced grade 1 or 2 CTCAE toxicities (dysphagia G1