ESTRO 2021 Abstract Book

S1244

ESTRO 2021

investigated in models using multiple measures analysis of variation and mixed linear regression.

Results Complete data was available in 8 bladder and 10 cervical cancer patients. Mean bladder volume was 143ml (95% CI, 137-150ml), and the volume range was large (35-645ml). There was no significant difference in bladder volume between bladder cancer and cervical cancer patients (median volume 120ml vs 90ml; p=0.2). When adjusting for intra-patient variability using the mixed linear model, there was no trend with tumour site or at any measured time point (Figure 1). However, bladder volume in the whole cohort was significantly higher in the second scan each week (122ml vs 108ml, p<0.001). The coefficient of variability (CV) for intra- patient variability was 0.47 (95% CI, 0.32-0.62) while that of inter-patient variability was 0.41 (95% CI, 0.28- 0.54). Figure 1: Box plot illustrating variation of bladder volume in all patients.

Conclusion Given that the bladder collects urine inflow, the significant increase in bladder volume between scan 1 and 2 each week was expected. Our data demonstrates significant variation between patients and across time points despite a standardised bladder filling protocol. Whilst it seems that for some patients the filling protocol produced consistent bladder volumes, we could not identify any variables allowing us to predict for this. We acknowledge that the sample size was low, but we believe this study adds weight to the adoption of adaptive radiotherapy with a “plan of the day” rather than relying on a drinking protocol to achieve an optimal target coverage throughout treatment. PO-1519 Efficacy and safety of radiotherapy for Epicondylitis Humeri (EPH) T. Latusek 1 , D. Gabryś 1 , G. Woźniak 1 , A. Krzywon 2 , A.J. Cortez 2 , L. Miszczyk 1 1 Maria Sklodowska-Curie National Research Institute of Oncology Gliwice Branch, Radiotherapy Department, Gliwice, Poland; 2 Maria Sklodowska-Curie National Research Institute of Oncology Gliwice Branch, Biostatistics and Bioinformatics, Gliwice, Poland Purpose or Objective A lot of non-malignant diseases are associated with painful inflammation of connective tissue which significantly reduce the quality of life of patients and impair their functioning. Some of these diseases can be successfully treated with irradiation. The aim of the study was to evaluate the effectiveness and safety of radiotherapy in EPH Materials and Methods The study was a retrospective analysis of clinical material, which included 51 cases. All patients were irradiated to a total dose of 6Gy given in 6 fractions five times weekly. Several aspects concerning: pain duration before RT, diagnostic imaging findings and adverse effects of RT were assessed. The effectiveness of radiotherapy was assessed using the numerical pain rating scale NRS (NRS-Numerical Rating Scale) as well as Patient Rated Elbow Evaluation (PREE) to evaluate functional outcome Results The analysis covered a group of 51 cases (43 patients), including 31 women (61%) and 20 men (39%). The follow-up was 2 years. Taking into account the NRS scale, the mean value of pain after RT decreased in relation to the baseline value during the follow-up period. Before RT, the mean NRS score was 8.3. Immediately after RT and 3 months after RT, scores of 6.3 and 2.4 were recorded, respectively. During the control period 6-24 months, the mean value of pain according to NRS was 2 and subsequently 2.2 Before starting the therapy, the average value according to PREE was 67. Immediately after RT and 3, 6, 12 and 24 months after RT the mean value according to PREE was lower at 49.6, 16.1, 13.0, 13.5 and 13.1, respectively. After 24 months pain relief was observed in 81,6% patients, including 56% with complete pain relief. No adverse effects and secondary malignances were observed Conclusion Radiotherapy for Epicondylitis Humeri is an effective treatment providing pain relief and functional improvement without significant toxicity and secondary malignances. No significant changes in imaging studies and duration of symptoms less than 12 months are positive predictive factors for the effect of therapy

PO-1520 FAPI-PET/CT improves diagnostic staging and radiotherapy planning of Adenoid Cystic Carcinomas M. Syed 1 , M. Röhrich 2 , F. Giesel 2 , J. Liermann 1 , P. Choyke 3 , H. Kauczor 4 , J. Debus 1 , U. Haberkorn 2 , S. Adeberg 1