ESTRO 2020 Abstract Book

S663 ESTRO 2020

involved was single in 13 patients and multiple (2–5) in 8 patients. The median GTV was 9.6 cc (range: 1.4–80.0 cc). Seventeen patients (81.0%) received IMRT including in the regional lymph node area. Median IMRT dose to GTV was 60 Gy (range: 50 to 70 Gy). Twelve patients (47.1%) received some systemic therapy after diagnosis for oligo- recurrence. All patients completed the course of IMRT. Median follow-up period after their IMRT was 33.7 months (range: 6.2–71.3 months). At the last follow-up, 9 out of the 21 patients (43%) achieved progression-free survival. Two patients had exclusively in-field progression, 3 had out-of-field progression, and 7 had both. The three-year overall survival (OS) rate, in-field progression free survival (IFPFS) rate and out-of-field progression free survival (OFPFS) rate were 75%, 52% and 44%, respectively. Statistical analysis showed the following: 1) lower total dose and larger GTV size were significantly associated with worse OS rates, respectively, 2) adenocarcinoma and lower total dose were significantly associated with worse IFPFS rates, respectively, 3) older age and SCC were associated with better OFPFS rate, respectively. No patients experience grade 3 or higher acute or late adverse events except one, who developed acute grade 3 IMRT could be effective and safe for patients with lymph node oligo-recurrence and a curative treatment option for selected cases. Tumor dose escalation sparing normal tissue using IMRT technology may provide better overall and in-field progression-free survival. PO-1259 Adoption of single-fraction radiotherapy for uncomplicated bone metastases in a tertiary centre C. Peters 1 , J. Vandewiele 1 , Y. Lievens 1 , M. Van Eijkeren 1 , V. Fonteyne 1 , T. Boterberg 1 , P. Deseyne 1 , L. Veldeman 1 , W. De Neve 1 , C. Monten 1 , S. Braems 1 , F. Duprez 1 , K. Vandecasteele 1 , P. Ost 1 1 University Hospital Ghent, Radiation Oncology, Ghent, Belgium Purpose or Objective Single-fraction radiotherapy (SFRT) offers equal pain relief for uncomplicated painful bone metastases as compared to multiple-fraction radiotherapy (MFRT). Despite this evidence, the adoption of SFRT has been poor with published rates of SFRT for uncomplicated bone metastases ranging from <10% to 70%. We aimed to evaluate the adoption of SFRT and its evolution over time following the more formal endorsement of the international guidelines in our centre starting from 2013. Our centre is located in a country where there is no financial incentive for MFRT over SFRT. Material and Methods We performed a retrospective review of fractionation schedules at our centre for painful uncomplicated bone metastases from January 2013 until December 2017. Only patients treated with 1x8Gy (SFRT-group) or 10x3Gy (MFRT-group) were included. We excluded other fractionation schedules, primary cancer of the bone and post-operative radiotherapy. Uncomplicated was defined as painful but not associated with impending fracture, existing fracture or existing neurological compression. Temporal trends in SFRT/MFRT usage and overall survival were investigated. We performed a lesion-based patterns of care analysis and a patient-based survival analysis. Mann-Whitney U and Chi-square test were used to assess differences between fractionation schedules and temporal trends in prescription, with Kaplan-Meier estimates used for survival analysis (p-value <0.05 considered significant). Results Overall, 352 patients and 594 uncomplicated bone metastases met inclusion criteria. Patient characteristics were comparable between SFRT and MFRT, except for age (table 1). Overall, SFRT was used in 92% of all metastases compared to 8% for MFRT. SFRT rates increased throughout leukopenia. Conclusion

the study period from 85% in 2013 to 95% in 2019 (p = 0.06) (figure 1). Re-irradiation rates were higher in patients treated with SFRT (14%) as compared to MFRT (4%) (p = 0.046). Which may indicate a lower threshold for re- irradiation if initial pain relief is inadequate. Four-week mortality and median overall survival did not differ significantly between SFRT and MFRT (17% vs 18%, p = 0.8 and 25 weeks vs 38 weeks, p = 0.97 , respectively). Conclusion Adherence to the international guidelines for SFRT for uncomplicated bone metastasis was high and increased over time to 95%, which is the highest reported rate in literature.

PO-1260 30-Day Mortality Following Palliative Radiotherapy M. Vázquez Varela 1 , M. Altabas Gonzalez 1 , A. Giraldo Marín 1 , V. Reyes López 1 , X. Maldonado Pijoan 1 , B. Navalpotro Yagüe 1 , M. Ramos Albiac 1 , R. Vergés Capdevila 1 , S. Benavente Norza 1 , S. Micó Milla 1 , R. Granado Carrasco 1 , J. Giralt López de Sagredo 1 1 Hospital Universitario Vall d'Hebron, Radiation Oncology, Barcelona, Spain Purpose or Objective Studies have shown that physicians tend to be overoptimistic at predicting survival. 30-Day Mortality (30DM) is a parameter with widespread use as an indicator of avoidance of. Predictive variables related to 30DM in palliative radiotherapy have been reported on the literature. Furthermore, a significant increase in symptoms and disability has been suggested to occur in the last 3 months of life. Our purpose is to determine the 30DM