ESTRO 2020 Abstract Book

S606 ESTRO 2020

PO-1151 Is the dose-distribution in bladder really unimportant for GU toxicity in prostate cancer patients? W. Majewski 1 , A. Napieralska 1 1 Maria Sklodowska-Curie Memorial Cancer Center and Institute of Oncology, Radiotherapy Department, Gliwice, Poland Purpose or Objective In patients with prostate cancer there is a well- documented dose-volume-effect for rectal toxicity. However, data on GU toxicity did not reveal a clear dose- volume-effect relationship in a bladder. We assumed that a lack of such relationship may be caused by many confounding factors, which influence GU toxicity. Therefore the analysis was restricted to patients presenting no dysuria and no urinary infections at the beginning of radiotherapy which are factors that seem to In a group of 180 patients with prostate cancer treated with a radical 3DCRT or IMRT between 2008 and 2011, 99 patients (55%) had no dysuria and urinary tract infections before radiotherapy. Those patients formed the group for further analysis. Mean patients’ age was 68 years, there were 16%, 39% and 45% of patients in low, intermediate and high-risk group, respectively. Patients were treated with conventionally fractionated radiotherapy to the total dose of 76 Gy with 2 Gy per fraction, in 45% of patients pelvic lymph nodes irradiation was performed. Patients were planned and treated with a comfortably filled bladder (2 h after urination). Bladder dose constraints were as follows: V70 ≤20%, V60 ≤35%, V50 ≤50%. We assessed Grade 2+ acute GU toxicity and Grade 2+ late GU toxicity in relation to various parameters representing dose distribution in the bladder: volume of the target (CTV), V30-V75Gy, Dmax, D2% (near maximum dose). The evaluation of the dose-effect relationship was performed with logistic regression for acute toxicity and Cox proportional hazard model for late toxicity. Results Acute G2+ GU toxicity was observed in 37 patients (37%), and late G2+ GU toxicity was observed in 7 patients (7%) with an actuarial rate of 7% at 5-years. With respect to the acute toxicity only D2% had statistically significant (p=0.033) impact on the incidence of acute G2+ GU toxicity. The volume of the target (CTV) had some statistical trend (p=0.098). With respect to late G2+ GU toxicity only D2% had statistically significant impact (p=0.017) with some statistical trend for Dmax (p=0.074). Conclusion In the purified group of patients presenting neither dysuria nor urinary infections before RT some impact of the dose distribution in the bladder on GU radiation toxicity may be observed. Only very high-dose regions were important. Probably during treatment planning much effort should be put on reducing very high dose volumes and “hot-spots” because they seem to be more important than other dose- volume parameters in a bladder. PO-1152 Postoperative Prostate Cancer treated with High-dose Radiotherapy. E. Amaya 1 , P. Samper 1 , M. Hernández 1 , M.D. De Las Peñas 1 , J. Zapatero 1 1 Rey Juan Carlos Universitary Hospital., Radiation Oncology, Madrid, Spain Purpose or Objective To analyze and release our center outcomes about prostate cancer patients with Biochemical Failure (BF) after radical prostatectomy, treated with postoperative high-dose radiotherapy through daily IGRT system. Material and Methods Restrospective study of 57 patients with a mean age 62.39 (range 49-72) years. All patients underwent surgery and influence GU toxicity. Material and Methods

anatomopathological results were: 22 (38,6%) pT3a, 12 (21,1%) pT3b, 6 (10,5%) pN1 and 10 (17,5%) pNx, 6 (10,5%) Gleason Score (GS) <6, 33 (58%) GS = 7 and 16 (28%) GS > 8; 22 (38,6%) R0 and 34 (59,6%) R1, 43 (75,4%) positive perineural invasion (PNI) and 13 (22,8%) positive lympovascular invasion (LVI). Postoperative PSA was 0.61 (range, 0.01-17.66). In 54 patients, imaging test showed 44 (77.2%) local failure (LF), 2 (3.5%) local and lymphatic node failure, 5 (8.8%) lymphatic node failure, and 2 (3.5%) distance disease. PTV included was: 28 (49.1%) tumor bed alone, 20 (50.9%) tumor bed and pelvic nodes, and 6 of them received treatment about metastasis (4 lymphatic and 2 bones metastasis). RT treatment was done through VMAT-daily IGRT system with a total dose of 74Gy/37 fractions. Toxicity was evaluated with CTC-AE v4. Statistical analysis was performed with SPSS 22.0 software package (IBM SPSS, Inc., Chicago, IL, USA). Results With a mean follow up of 31.2 months, 18 (31.6%) patients had biochemical failure after RT treatment. FBFS (Free Biochemical Failure Survival) was 67.9% and mean survival 43 months. Most important prognostic factor for BF was PSA preRT <0.5 ng/ml vs >0.51 ng/ml, 23.7% vs 57.1% respectively (p= 0.027). FBFS was 76.3% in PSA preRT <0.5 group and 42.9% in PSA preRT >0.51 group and mean FBFS 49.76 months (IC95% 41.3-58.2) in PSA preRT <0.5 and 28.9 months (IC95% 6.57-16.12) in PSA preRT >0.51, p = 0.021 (Log Rank) (Figure 1) . There are no other significant prognostic factors for BF. No patient had LF but there was 5 (8.8%) with lymphatic nodes failure, 7 (12.3%) with distance disease and 6 (10.5%) with oligorrecurrence. 1.8% of treated patients had genitourinary (GU) acute toxicity G3 and 26.3% was G1-2. GU chronic toxicity G1-2 was 15.8% and 3.5% G3. There was only gastrointestinal acute toxicity G1 3.5% and no chronic toxicity. Disease free survival (DFS) was in PSA preRT <0.5 68.4% and 64.3% in PSA preRT >0.51 and mean DFS 35.85 months (IC95% 29.71-42) in PSA preRT <0.5 and 42.71 months (IC95% 30.18-55.25) in PSA preRT >0.51.

Conclusion High-dose RT with IGRT in postoperative prostate cancer patients is a safe and effective treatment for local control of tumor bed with an excellent acute and chronic toxicity results. PO-1153 Isolated bone metastases in prostate patients: preliminary analysis from two phase I trials on SRS F. Deodato 1 , A. Re 1 , A. Ianiro 2 , M. Boccardi 1 , M. Ferro 1 , S. Cammelli 3 , C. Romano 2 , V. Picardi 1 , D. Traficante 4 , A. Di Lallo 5 , M. Buwenge 3 , M. Ciuffreda 6 , M. Ferro 1 , S. Cilla 2 , V. Valentini 7 , A.G. Morganti 3 , G. Macchia 1 1 Università Cattolica S. Cuore- Fondazione Giovanni Paolo II, UO di Radioterapia, Campobasso, Italy ; 2 Università Cattolica S. Cuore- Fondazione Giovanni