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

Phase IIIb randomized stratified open-label comparative 2-arm superiority study with a pre-set non-inferiority boundary. Registered GnRH antagonists, degarelix, will be given at the dose of 240 mg given as two subcutaneous injections of 120 mg at a concentration of 40 mg/mL on day 1, followed by 80 mg given as one subcutaneous injection at a concentration of 20 mg/mL every 28 days (±2 days). External beam radiotherapy (EBRT) to a total dose of 78-80 Gy, delivered as one daily fraction, five days a week, started between d1 and months 6 of the androgen deprivation therapy as per institution policy. The irradiation is the same as in the reference therapy arm. The minimum duration of androgen deprivation with GnRH agonist or antagonist therapy is 18 months. For each patient, the duration of therapy must be elected upfront by the treating physician among three possible options: 18, 24 or 36 months. The institution shall also declare upfront the duration of the neoadjuvant treatment they intend to deliver to each patient (between 0 and 6 months). The primary endpoint is progression-free survival defined as the time in days from randomization to death, clinical or biochemical progression, whichever comes first. Where * PSA progression based on Phoenix definition, i.e. a rise by 2 ng/mL or more above the nadir PSA (Ref. 17) confirmed by a second value measured minimum 3 months later * Clinical progression is defined as onset of obstructive symptoms requiring local treatment and demonstrated to be caused by cancer progression or evidence of metastases detected by clinical symptoms and confirmed by imaging * Start of another line of systemic therapy in absence of progression * Death due to any cause Secondary endpoints: * Clinical progression-free survival * Time to next systemic anticancer therapy (including secondary hormonal manipulation) * Proportion of patients switching from GnRH antagonists to GnRH agonists and total effective duration of treatment with the originally allocated drug. * Overall survival * Cancer specific survival * PSA at six months after completion of RT Safety will be scored by the CTCAE version 4.0. The major safety endpoints in this study are * the incidence of clinical cardiovascular events - CCE (i.e. arterial embolic or thrombotic events, hemorrhagic or ischemic cerebrovascular conditions, myocardial infarction, and other ischemic heart disease) in patients who had cardiovascular events before entering the trial and in those without such events. * Incidence of urinary tract infection