ESTRO 36 Abstract Book

S722 ESTRO 36 2017 _______________________________________________________________________________________________

was observed between pain response and ALP response in this cohort. EP-1360 Stereotactic body radiotherapy for oligometastatic prostate cancer recurrence after local treatment. P.A. laurent 1 , E. Martin 1 , F. Cousin 2 , M. Quivrin 1 , F. Bidault 3 , F. Mazoyer 3 , A. Bertaut 2 , G. Crehange 1 1 Centre Georges-François Leclerc, Radiation Oncology, Dijon, France 2 Centre Georges-François Leclerc, Statistics, Dijon, France 3 Centre Georges-François Leclerc, Medical Physics, Dijon, France Purpose or Objective To analyse patients treated by stereotactic body radiotherapy (SBRT) for a node or bone oligometastatic recurrence of a prostate cancer (Pca) previously locally treated, and identify possible pronostic factors of early biochemical failure (BF) after SBRT. Material and Methods In this retrospective study, we analyzed castrate and non- castrate patients treated by SBRT between November 2011 and April 2016 for 1 to 3 metastases, bone or node, diagnosed on a positron emission tomography - computed tomography (PET-CT) or on a bone-scintigraphy with technetium-99, following biochemical recurrence of a prostate cancer after a local curative treatment. Recurrence-free survival (RFS) was the primary end-point defined as the time interval between the first day of SBRT and biochemical failure, defined as 2 consecutive elevations of PSA with last dosage superior to PSA dosage before treatment, or clinical failure, defined as new metastases found on an imaging check-up (PET-CT or scintigraphy). PSA dosage before SBRT, type of metastase (bone or node), number of lesions treated in SBRT, patient's ages, nadir of PSA after SBRT, and concomittant androgen deprivation therapy (ADT) were analyzed in univariate and multivariate logistic regression to identify pronostic factors of poor response to SBRT. Results With a median follow-up from time of SBRT of 12 months, we treated 40 patients and 56 metastatic lesions, with a local-control rate of 85%. 19 patients were treated for 1 to 3 bone lesions and 21 patients for 1 to 3 node lesions. 8 patients with bone oligo-metastasis and 13 patients with node oligometastasis had a recurrence. The primary involved metastatic sites were lymph nodes ( 52 %) and bone ( 52 %), with 3 patients having both node and bone recurrence . A 2 nd and 3 rd course of radiotherapy was delivered in 8 and 1 patients respectively. Median RFS was 345 days (134 ; 426) in the node metastatic group and 494 days (85 ; 877) in the bone metastatic group. On bivariate analysis, a PSA nadir up to 0,51 ng/mL after SBRT was identified as a pronostic factor of low RFS. This result was not confirmed in multivariate analysis. There might be a significative difference in RFS between node group and bone group. Conclusion There might appear that patients treated by SBRT for node oligometastatic prostate cancer recurrence after a local curative treatment could have a lower recurrence- free survival than patient treated for bone oligometastatic disease in the same conditions. This observation justifies further analysis. Ep-1361 Prostate sbrt in 5 fractions , report of 185 patients and late toxicity analysis. P. Castro Peña 1 , O. Muriano 1 , A. Henao 1 , P. Murina 1 , C. Niño de Guzman 1 , D. Venencia 1 , S. Zunino 1 1 Instituto Privado de Radioterapia, Radiation Oncology, Cordoba, Argentina

To analyze late urinary and rectal toxicity in patients with prostate cancer who underwent SBRT 5 fractions Material and Methods Among November'13 and June'15, 185 patients with positive biopsy of prostate cancer were treated; PSA- baseline mean = 14.99 ng / ml [0.42-123.3] and prostate volume average = 52.6 g [20.6-134].All were irradiated with SBRT technique in 5 fractions (every other day), according to institutional protocol. IGRT (intra and interfraction) were ExacTrac based, 2 weeks before, 5 intraprostatic titanium fiducial markers were implanted. Virtual simulation based on CT-scan was done every 1mm at prostate level. Drawing volumes and dosimetry planning were done at Iplan-Net system. Prescribed dose at 95% PTV-prostate = 40 Gy or 36.25, depending the risk group.Patients were irradiated with Novalis Tx (BrainLab- Varian) technology, high-resolution multileaf collimator (HDMLC) with leaf of 2.5mm. Planned and irradiated with IMRT-dynamics technique, using 9 portals of 6 MV beams.Genitourinary toxicity (GU) was evaluated using the scale IPSS (International Prostate Symptom Score) and gastrointestinal (GI) according to RTOG criteria. Results The mean age was 69.1 years [48.1-86.6]. The distribution by risk group was 12.3%, 59.5% and 28.2% low, medium and high respectively.Mean follow-up = 15.1 months [3.8- 31.7]The mean IPSS was before SBRT = 6.2 [0-35]. Post- SBRT = 5.6 [0-34]; 5.1 [0-31]; 5.6 [0-30]; 4.8 [0-22] and 5.6 [0-28] for 2; 6; 12; 18 and 24 months respectively.The rate and extent of post-SBRT rectal toxicity was at 2 months G0 = 80.5%; G1 = 14.1% = 5.4% and G2. At 6 months: G0 = 85%; G1 = 4.1%, 4.9% and G2 = G3 = 1.6. At 12 months: G0 = 92.1%; G1 = 3.3%; G2 = 2.6%, G3= 0.7 and G4 = 1.6% At 18 months: G0 = 96.4%; G1 = 2.4%; G2 = 1.2. At 24 months: G0 = 97.3%; G1 = 2.7%; G2 = 0 Conclusion According to the presented results we can strongly suggest that Prostate SBRT- Novalis based platform is suitable for a patient acceptable toxicity rate EP-1362 Correlations between dose to small intestine and bladder volume in patients receiving pelvic IMRT M. Alfayez 1 , A. Sadozye 1 1 Beatson West of Scotland Cancer Centre, clinical oncology, Glasgow, United Kingdom The use of IMRT to treat various tumour sites has gained wider acceptance in recent years due to its ability to decrease the radiation dose to organs at risk. Various manoeuvres have been implemented to reduce the doses to organs at risk (OAR), such as the small bowel. Aims/Objectives We evaluated the effect of bladder filling on dose distributions for the small bowel as measured by V20, V30, V40 and V50. Material and Methods We studied sixty patients undergoing pelvic IMRT (pelvic nodes plus Prostate & Seminal Vesicles) to treat prostate cancer. The minimum dose to the PTV was 95% of the prescribed dose (7200 cGy in 32 fractions). All patients were scanned with a full bladder. PTV and OARs, including the small bowel were contoured by 6 different clinical oncologists to reflect day-to-day practice. Bladder volumes, dose-volume histograms (DVH), V20, V30, V40 and V50 for the small bowel were obtained for each We ran the Pearson correlation coefficient to measure the strength of the linear relationship between the bladder volume and the dose to the small bowel. Results showed a negative correlation between the bladder volume and the dose to the small bowel (p< 0.0001). Conclusion Purpose or Objective Background patient. Results

Purpose or Objective