Comparison of Intermittent Androgen Deprivation Therapy With or Without Irradiation Recovery in Prostate Cancer Patients

Metastatic prostate cancer has traditionally been regarded as an incurable dissemination of disease, and treatment is focused on delaying progression rather than eliminating all tumor burden. Local therapies, and specifically radiotherapy, have been directed at quality of life endpoints and not at improving survival. However, advances in imaging and systemic therapy have identified a population of 'oligometastatic' patients who have a lower burden of metastatic disease (usually ≤5 lesions), who may present an exception. This condition is hypothesized to occupy the hinterland between incurable metastatic disease and locoregional disease, where micrometastatic disease is assumed to exist and yet remain eradicable. Oligometastases can be detected using standard imaging but the sensitivity of these exams is very low for patients with a PSA below 10 ng/ml. In France, FCH PET imaging is now routinely available in a large majority of cancer centres. More recently, PSMA PET imaging has been developed. Since most oligometastases are now discovered at a time when conventional imaging is unable to detect metastases, we must rely on the literature regarding purely biochemically-relapsing prostate cancer patients. Three strategies have been explored: (i) observation until symptoms develop, (ii) early intermittent Androgen Deprivation Therapy (IADT) and (iii) continuous Androgen Deprivation Therapy (ADT). Recent data suggest that, of the three strategies, early intermittent ADT was superior in term of overall survival to observation in controlling metastatic prostate cancer, and this effect was similar in the biochemically-relapsing prostate cancer patient population. This phase III study will explore the role of salvage pelvic IG-IMRT combined with intermittent ADT (IADT) in pelvic oligometastatic patients in prolonging the first failure-free interval between the first and the second intermittent ADT courses.