ESTRO 2020 Abstract book

S690 ESTRO 2020

significant prognostic factors for local control (table 1). For overall survival, significant prognostic factors were age, smoking and WHO-PS (table 1). Acute treatment- related toxicity was generally mild with only 2.5 % of patients experiencing grade 3 GU toxicity and 1 % grade 3 GI toxicity. However, grade 2 toxicity was more preponderate with 15 % of patients experiencing grade 2 GI and 33 % of patients experiencing grade 2 GU toxicity. When comparing the different groups, significantly more grade 2 GI toxicity was noted in the CRT-group compared to the RT-only regimens but GU toxicity did not differ.

Median age at presentation was 69 years (range 16-89). Twenty-six percent of patients had a prior history of pelvic RT, and 37% were previous smokers. Main presenting symptoms at diagnosis were hematuria (52%), pelvic pain (27%), and both (10%). AJCC 8 group stage II, III and IV at diagnosis were 21%, 63% and 16%, respectively. Treatment modalities included surgery alone (45%), surgery plus neo- or adjuvant-chemotherapy (17%), surgery neo- or adjuvant-RT (11%), RT with concurrent chemotherapy (4%), neoadjuvant chemotherapy plus surgery plus adjuvant RT (2%) and palliative treatment (21%). Rates of local and distant recurrences were 49% and 37%, respectively. Five-year OS and PFS were 66.5% and 37.6% respectively. Median PFS for T2-category was not reached and for T3-T4 was 8.4 months (p=0.059). No statistically significant differences in PFS between treatment modalities were observed. Conclusion Primary SUB is an heterogeneous disease group, commonly presenting at advanced stages and exhibiting aggressive disease trajectory. Contrasting with UC, the primary pattern of recurrence of SUB is local, suggesting the need for multimodal approaches. Continuous international collaborative efforts seem warranted to provide guidance on how to best tailor treatments based on SUB-specific indices. PO-1220 Organ-preserving treatment for muscle- invasive bladder cancer: outcomes and prognostic factors M. Franckena 1 , N. Verschoor 2 , J. Boormans 3 , W. Heemsbergen 4 1 Erasmus Medical Center Rotterdam Daniel den Hoed Cancer Center, Department of Radiation Oncology, Rotterdam, The Netherlands ; 2 Erasmus Medical Center Rotterdam, Radiation Oncology, Rotterdam, The Netherlands ; 3 Erasmus MC Medical Center, Urology, Rotterdam, The Netherlands ; 4 Erasmus MC Medical Center, Radiation Oncology, Rotterdam, The Netherlands Purpose or Objective Objective: Organ-preserving treatment strategies (OPTS) for localized muscle invasive bladder cancer has become an acceptable alternative in selected patients instead of the standard of radical cystectomy. Clinical experience from large patient series is currently limited. Here we report on the outcomes and prognostic factors of OPTS, which may further guide treatment decisions in the context of the aging bladder cancer population where careful weighing of costs and benefits of treatment options will have to be made by both patient and physician. Material and Methods We performed a single-center retrospective cohort study comprising 248 patients with bladder cancer (T1-4N0M0), receiving external beam radiotherapy, preferably with radio- sensitizing chemotherapy (5FU/MMC) between 01- 2010 and 12-2017 at Erasmus Medical Center Rotterdam. Patients received 66 Gy in 33 fractions but for less fit patients, 63 Gy in 28 fractions was offered. We evaluated local control, acute treatment-related gastro-intestinal and genito-urinary toxicity (CTCAE V4), and survival. Results Median follow-up was 19.7 months (range: 0-60). Ninety- five % of patients completed treatment. As expected, median age, WHO performance status (WHO-PS) and Charlson Comorbidity index increased going from most preferred to least OPTS. Major tumor-related prognostic factors (tumour stage, tumor grade and presence of hydronephrosis) were equally distributed over subgroups. Local control (LC) and overall survival (OS) for the 66 and 63 Gy groups (n = 97 and n = 67) was significantly worse compared to the CRT-group (n=84), also after adjustment for disease characteristics. LC rates at 2 years were 81 %, 58 %, and 46 % respectively. OS rates at 2 years were 70 %, 48 %, and 37% respectively. We identified WHO-PS, Age as

Conclusion (Chemo)radiation in elderly and medically less fit patients was associated with high treatment compliance, acceptable toxicity profile and fair local control and survival rates. Even in the radiotherapy only group, an acceptable local control rate was achieved, justifying such a treatment in this patient population. Unfortunately, no predicting factors for acute toxicity could be identified. PO-1221 Dose-volume predictors of distal urethral toxicity after PDR brachytherapy for penile carcinoma S. Achkar 1,2 , R. Bourdais 1 , R. Sun 1 , T. Kumar 1 , M. Kissel 1 , T. Felefly 1 , M.H. Ta 1 , F.A. Pounou Kamga 1 , A. Escande 1 , E. Deutsch 1 , C. Haie-Meder 1 , C. Chargari 1 1 Gustave Roussy, Radiation oncology department, Villejuif, France ; 2 Hôtel-Dieu de France, Radiation Oncology department, Beirut, Lebanon Purpose or Objective Interstitial brachytherapy is a conservative treatment approach for localized penile cancer providing good local control. Dose constraints for distal urethra in this procedure are lacking. The aim of this study is to report our experience with pulse dose rate interstitial brachytherapy (PDR-BT) in the treatment of penile cancer and to evaluate dose-volume predictors of late urethral toxicity for potential use in clinical practice. Material and Methods The medical records of 65 patients treated with PDR-BT for localized squamous cell carcinoma of the glans penis in our institution between July 2008 and February 2019 were retrospectively reviewed. All patients underwent circumcision followed by PDR-BT. Interstitial needles were implanted according to the Paris system rules. Toxicity was graded according to Common Terminology Criteria for Adverse Events (CTCAE) v4.0. Univariate and multivariate analyses were performed to determine predictors of survival and toxicity among clinical and dosimetric characteristics. Results Median age at diagnosis was 64 years (range: 36-85 years). Median initial tumor greatest diameter was 25 mm (10-50 mm). Eight patients (12%) presented initially with inguinal