ESTRO 2020 Abstract book

S711 ESTRO 2020

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 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 followed by palliative radiotherapy in our center and to indentify predictors related to this parameter. As a secondary endpoint, we wanted to estimate overall survival at three months (3mOS). Material and Methods We conducted a retrospective cohort study including patients treated with palliative intent in our center from January to December 2018. Data related to clinical features and radiotherapy treatment were collected and used to compare two groups defined by their condition at the cut-off of 30 days: dead or alive. Chi-square test and logistic regression model were used to assess the impact of the studied variables on 30DM. Kaplan-Meier and log- rank test were used for a survival analysis at 3 months. 30DM and 3mOS were calculated from the beginning of the treatment to the last follow-up. Results Out of 1287 treatments, 593 were of palliative intent to 394 eligible patients with a median follow-up of 4 months. 30DM rate was 15% (59 patients) with a median time to death of 18 days (range 4-30). Characteristics of the sample according to 30DM are shown in table 1. 30-day survivors were treated with a higher number of fractions and showed a higher rate of responses to treatment. Clinical features as male sex (odds ratio [OR], 3.29, 95%CI: 1.68-6.43; p<0.001), ECOG 2-3 (Eastern Cooperative Oncology Group) (OR 4.35, 95%CI 2.39-7.92; p<0.001), KPS<70% (Karnofksy Performance Status) (OR 4.06, 95%CI 2.16-7.59, p<0.001) were significantly related to 30DM in the univariate analysis. Primary site was related to 30DM in the comparative analysis (Table 1), but only gastrointestinal (OR 5.16, 95%CI 1.36-19.60, p=0.016), lung (OR 5.483, 95%CI 1.36-18.88), prostate (OR 4.033, 95%CI 1.01-16.09, p=0.048) and melanoma (OR 12.4, 95%CI 1.966-78.196, p=0.007) were predictors of 30DM. Male sex, ECOG, Karnofsky and the presence of visceral disease were identified as an independent factor related to 30DM in the multivariate analysis. 3mOS was 43.7%. Survival curves