Trial Comparing Irradiation Plus Long Term Adjuvant Androgen Deprivation With GnRH Antagonist Versus GnRH Agonist Plus Flare Protection in Patients With Very High Risk Localized or Locally Advanced Prostate Cancer

Inclusion Criteria: * Histologically confirmed diagnosis of prostate adenocarcinoma * PSA ≥ 10 ng/ml and two of the following 4 criteria: * PSA ≥ 20 ng/ml, * Gleason sum ≥ 8, * cN1 (regional LN with a short axis length \>10mm by CT scan or MRI) or pathologically confirmed lymph nodes (pN1), * cT3-T4 (by MRI or core biopsy) (i.e. If PSA≥ 20 ng/ml then only one of the other 3 risk factors is needed) * M0 by standard imaging work-up (see chapter 6.1.1.1) * Testosterone ≥ 200 ng/dl * Adequate renal function: calculated creatinine clearance ≥ 50 mL/min (Appendix D) Magnesium and potassium within normal limits of the institution or corrected to within normal limits prior to the first dose of treatment. * Patients with prolonged QT-intervals due to prescribed Class IA (quinidine, procainamide) or Class III (amiodarone, sotalol) antiarrhythmic medication must be carefully evaluated for GnRH-agonist or GnRH antagonist use, because these drugs may prolong the QT-interval. * WHO Performance status 0-1 * Age ≥ 18 and ≤ 80 years * Participants who have partners of childbearing potential must use adequate birth control measures, as defined by the investigator, during the study treatment period and for at least 3 months after last dose of study treatment. A highly effective method of birth control is defined as those which result in low failure rate (i.e. less than 1% per year) when used consistently and correctly * Before patient registration/randomization, written informed consent must b…