Abstract Book

S851

ESTRO 37

EP-1580 Patterns of androgen deprivation therapy use with radiotherapy in post-prostatectomy setting W.L. Ong 1 , F. Foroudi 1 , S. Evans 2 , J. Millar 3 1 Olivia Newton John Cancer and Wellness Centre- Austin Health, Department of Radiation Oncology, Heidelberg, Australia 2 Monash University, Department of Epidemiology and Preventive Medicine, Prahran, Australia 3 Alfred Health, Radiation Oncology Service, Prahran, Australia Purpose or Objective There is increasing evidence that androgen deprivation therapy (ADT) given with radiotherapy (RT) following radical prostatectomy (RP) is associated with overall survival benefits. We aim to evaluate the practice pattern of ADT use in a population-based cohort of Australian men with prostate cancer (CaP) who had RT post-RP. Material and Methods This is a prospective cohort of men with CaP captured in the Prostate Cancer Outcome Registry Victoria (PCOR- Vic), who were treated with RT post-RP, between January 2010 and December 2015. The primary outcome is whether ADT was used with RT. Multivariate logistic regression was used to identify factors influencing the use (or omission) of ADT with RT post-RP. Results 509 men were included in the study – 116 (23%) had organ confined disease (pT2), 242 (48%) had extracapsular extension (pT3a), 146 (29%) had seminal vesicle invasion (pT3b), and 5 (1%) had bladder/ rectum invasion (pT4). CaP were classified based on ISUP grading – 18 (4%), 140 (28%), 175 (34%), 43 (8%) and 133 (26%) had ISUP Grade 1, 2, 3, 4, and 5 respectively. 24 (5%) men had nodal involvement on node dissection (pN1), while 328 (64%) had positive surgical margins. The median time from RP to RT was 8 months (range=1.5-64 months). Overall, 78 (15%) patients had ADT with RT. Men who had ADT were older (mean age 64.5) compared to men who did not have ADT (mean age 62.2) (P=0.004). Men with higher ISUP Grade were more likely to have ADT – 11% ISUP Grade 1, 3% ISUP Grade 2, 22% ISUP Grade 3, 17% ISUP Grade 4, and 32% ISUP Grade 5 (P<0.001). Men with non-organ confined disease were more likely to have ADT (8% pT2, 12% pT3a, 27% pT3b, 20% pT4, P<0.001). Men with N1 disease were also more likely to have ADT (50%) compared to N0 disease (14%) (P<0.001). There is no significant difference in ADT use between men with positive (16%) vs. negative (13%) surgical margin (P=0.3). Men treated in regional centres (28%) were more likely to have ADT compared to those treated in metropolitan centres (13%) (P=0.002). In multivariate analyses, only nodal status and treatment centre were independently associated with ADT use – men with N1 disease (OR=3.7, 95%CI=1.5-9.3, P=0.005), and those treated in regional centres (OR=2.2, 95%CI=1.2-4.3, P=0.02) were more likely to have ADT with RT. Conclusion This is the largest Australian population-based study reporting the contemporary patterns of ADT use with RT in the post-RP setting, with less than 1-in-6 men receiving ADT with RT. With long-term follow-up, it will be interesting to evaluate if the pattern of ADT use in a population-based real-life clinical setting translates into overall survival differences as observed in clinical trials.

EP-1581 Salvage brachytherapy and a rectal spacer in locally recurrent prostate cancer after radiotherapy G. Crehange 1 , L. Cormier 2 , A. Bertaut 3 , D. Peiffert 4 , M. Bolla 5 , O. Chapet 6 , E. Rio 7 , R. De Crevoisier 8 , E. Martin 1 , J.M. Cosset 9 1 Centre Georges-François Leclerc, Radiotherapy, Dijon, France 2 University Hospital François Mitterand, Urology, Dijon, France 3 Centre Georges-François Leclerc, Biosttistics, Dijon, France 4 Institut de Cancérologie de Lorraine, Radiation Oncology, Vandoeuvre-les-Nancy, France 5 CHU La Tronche, Radiation oncology, Grenoble, France 6 University Hospital Pierre Bénite, Radiation oncology, Lyon, France 7 Institut de Cancérologie de l'Ouest, Radiation oncology, Nantes, France 8 Centre Eugène Marquis, Radiation oncology, Rennes, France 9 Institut Curie, Radiation oncology, Parisf, France Purpose or Objective Salvage prostate permanent implant (sPPI) for locally recurrent prostate cancer after prostate dose-escalated radiotherapy or brachytherapy may harm the rectum. Material and Methods We enrolled 35 patients with local relapse after radiation therapy in a multicenter phase II trial. All of the patients had sPPI with I 125 seeds under transrectal US guidance. The minimal peripheral dose prescribed to the whole prostate or to the index lesion diagnosed on multiparametric MRI, if any, were 90Gy and 144Gy, respectively. At the end of each procedure, hyaluronic acid (HA) gel (Restylane® from Galderma, Uppsala) was injected into the rectoprostatic interface. This preliminary report focuses on the feasibility of HA gel into previously irradiated pelvic tissues and short-term toxicities at 6 months. Results Two patients (5.7%) refused sPPI after inclusion and were excluded. The median time between the primary biopsies and local failure was 8.0 years [2.5-17.4]. The primary irradiation was delivered using 3DRT in 12 patients, IMRT in 7 patients, 2D-RT in 3 patients (one unknown). The median dose delivered to the prostate was 74Gy [70-80]. Ten patients had prostate brachytherapy with I 125 seeds as the primary treatment with a median D90%= 172.5Gy [97.0-184.5] and a V100%= 96.5 [93.7-99.9]. The median PSA value at failure was 3.0 ng/mL (0.3-12.4). Thirty two patients had a multiparametric MRI at failure of whom 25 had an index lesion. At failure, 12 out of the 26 patients who had a rectoscopy (46.2%) had a rectitis : 11 grade 1 and 1 patient grade 2. The median sPPI D90% to the prostate was 109.0Gy (80.8-142.5) and the median D90 to the index lesion was 167.8Gy (102.5-189). Thirty-three patients (100%) had a successful HA gel implant and 18 patients had a space ≥5mm. The mean minimal and maximal distances between the posterior boundary of the prostate and the rectal outer wall were 12.2 mm (±18.0) and 24.2 mm (±33.9). The day of sPPI, the median D0.1cc to the rectum before HA gel was 100.0Gy [60.0-157.0] and the median RV100% was 0.1cc [0.0-1.9]. After coregistration between the post-HA gel MRI and the post- implant CT, the median D0.1cc to the rectum was 70.5Gy [32.0-169.0] and the median RV100% was 0.0cc [0.0-0.9]. At 6 months, 9 (27.3%) and 2 patients (6.1%) had grade 2