ESTRO 2020 Abstract book

S116 ESTRO 2020

Between April 2016 and December 2018, 100 men were treated in four academic centres. All patients were followed for a minimum of 6 months. At baseline, median age of the included patients was 73 years (range, 57‐84 years), median PSA level was 10.8 ng/mL (range, 3.0‐29.0 ng/mL) and 75.0% of the patients were classified as having high risk prostate cancer according to the EAU risk classification. Additionally, 44% was staged clinical tumour category cT3a. The median mean dose delivered to the visible tumour nodule(s) on multiparametric MRI was 44.7 Gy. The aimed dose of 50 Gy was in most cases not achieved, due to normal tissue constraints. No grade ≥3 acute genitourinary (GU) or gastrointestinal (GI) toxicity was observed. The acute (90 days after start of treatment) cumulative grade 2 GU and GI toxicity rates were 34.0% and 5.0%, respectively. The prevalence of grade 2 GU toxicity increased during treatment and reached a maximum at the end of treatment (25.5%). Thereafter, the prevalence of GU toxicity declined to 11.4%, 90 days after starting the radiation treatment. The prevalence of grade 2 GI toxicity did not exceed 5% at any time (Figure 1).

Radiation Oncology, Nancy, France ; 6 Centre Georges- François Leclerc, Radiation Oncology, Dijon, France ; 7 Centre Léon Bérard, Radiation Oncology, Lyon, France ; 8 Centre Jean Perrin, Radiation Oncology, Clermont- Ferrand, France ; 9 Clinique Pasteur, Radiation oncology, Brest, France ; 10 Clinique Pasteur, Radiation Oncology, Toulouse, France ; 11 Centre François Baclesse, Radiation Oncology, Caen, France ; 12 Centre Jean Bernard, Radiation Oncology, Le Mans, France ; 13 Institut de Cancérologie de l'Ouest, Biostatistics, Nantes, France ; 14 Institut de Cancérologie de l'Ouest, Radiation oncology, Nantes, France Purpose or Objective Oligorecurrent pelvic nodal relapse of prostatic cancer is a challenge for regional salvage treatments. We conducted OLIGOPELVIS – GETUG P07, a phase II trial of combined salvage radiotherapy and hormone therapy in oligorecurrent pelvic node relapses of prostate cancer (NCT02274779) Material and Methods OLIGOPELVIS – GETUG P07 was a prospective multi-center phase II trial investigating high-dose salvage pelvic irradiation with an additional dose to the fluorocholine- based positron-emission-tomography (FCH- PET)-positive pelvic lymph nodes (PLN), combined with six-month androgen blockade (LH-RH agonist or antagonist injections). The prescribed dose was 54 Gy in 1.8 Gy fractions with up to 66 Gy in 2.2 Gy fractions to the pathological PLN. Toxicity (CTCAE v4) and complete response rates (PSA < 0.20 ng/ml) were analyzed. The main objective was to assess biochemical-clinical failure defined by a cluster of events including PSA progression (≥25 % and ≥ 2 ng/ml above the nadir) or clinical evidence of local or metastatic progression or post- treatment initiation of hormonal therapy or prostate cancer-related death. We hypothesized that salvage treatment would achieve a 2-year relapse-free survival of 70 %. Results Seventy-four patients were recruited in fifteen French radiation oncology departments between August 2014 and July 2016. Seven were excluded before treatment because of violation of the inclusion criteria. The intention-to-treat analysis therefore included sixty-seven patients. Half of them had received prior prostatic/prostate bed irradiation. Median age was 67.7. Grade 2+ two-year urinary and intestinal toxicity were 10% and 2% respectively. At 2 and 3 years, 73.1 and 45.9% of patients achieved a persisting complete response respectively. After a median follow-up of 34 months, the 2-year progression-free survival rate was 77.6%. Median progression-free survival was 40.1 months. Conclusion Combined pelvic salvage radiotherapy and hormone therapy allowed for prolonged tumor control in oligorecurrent pelvic node relapses of prostate cancer with limited toxicity. OC-0211 Bladder and Urethra Subregions for Prediction of Urinary Toxicity: Insights from External Validation E. Mylona 1 , M. Ebert 2 , A. Kennedy 2 , J.W. Denham 3 , D.J. Joseph 4 , A. Steigler 3 , O. Acosta 1 , R. De Crevoisier 1 1 Université de Rennes 1, Ltsi, Rennes CEDEX, France ; 2 Sir Charles Gairdner Hospital, Department of Radiation Oncology, Western Australia, Australia ; 3 University of Newcastle, School of Medicine and Public Health, New South Wales, Australia ; 4 Sir Charles Gairdner Hospital, Department of Medicine and Surgery, Western Australia, Australia Purpose or Objective A recent voxel-based analysis of the dose to the bladder and the urethra allowed the identification of five subregions (Figure 1A) predictive of five specific urinary

Conclusion The phase II hypo-FLAME trial showed that a focal SBRT boost to the macroscopic tumour(s) in addition to whole gland prostate SBRT is associated with acceptable acute GU and GI toxicity. Furthermore, besides the potential benefit in tumour control by focal boosting and extreme hypofractionation, the associated reduction in fraction number is attractive to both patients and radiation oncology departments. OC-0210 Salvage radiotherapy in oligorecurrent pelvic node relapses of prostate cancer : a phase 2 trial S. Supiot 1 , D. Pasquier 2 , X. Buthaud 3 , N. Magne 4 , V. Becckendorf 5 , G. Crehange 6 , P. Pommier 7 , G. Loos 8 , A. Hasbini 9 , I. Latorzeff 10 , M. Silva 11 , F. Denis 12 , L. Campion 13 , L. Vaugier 14 , A. Blanc-Lapierre 13 1 Institut de Cancérologie de l'Ouest, Radiation Oncology, Angers, France ; 2 Centre Oscar Lambret, Radiation Oncology, Lille, France ; 3 Clinique du confluent, Radiation Oncology, Nantes, France ; 4 Institut de cancérologie de la Loire, Radiation Oncology, Saint- Etienne, France ; 5 Institut de Cancérologie de Lorraine,

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