First Line gastroeSOphageal metastatiC canceR primAry and disTant (if Oligometastatic) lEsions-directed Radiotherapy, a Multicentric, Phase III, Randomized Controlled Trial

Inclusion Criteria: * Patients diagnosed with gastroesophageal cancer (i.e.: esophagus, gastroesophageal junction, stomach), for both major squamous cell (SCC) and adenocarcinomatous (ADK) histologies, metastatic, candidate for first-line standard systemic treatment; either newly diagnosed in metastatic stage or first progression to metastasis. * Obtaining informed consent. * Patients \>18 years of age * ECOG 0-2 * Performance of imaging (CT with mdc, MRI with mdc, CT-PET with appropriate tracer) adequate for baseline local and systemic staging and likely to be similarly repeatable at 6 and 12 months after randomization * Confirmation at the time of randomization, by the Radiation Therapy Center, that all potentially planned treatments can be performed for the patient (if enrolled in experimental arm) within a maximum of 25 days total before referral to the Medical Oncology Center for systemic therapy Exclusion Criteria: * Metastatic picture of line following the first * Technical or organizational inability to the eventual deadline for radiation treatments within 25 days of randomization * Inability to express independent consent to treatments * Pregnancy * Patient in hospice or with prognosis \< 6 months * Predicted unavailability for follow-up at 6 months * Absence of adequate or likely non-repeatable pretreatment imaging study at 6 and 12 months * Previous radiation therapy * Previous radiometabolic therapy * Inability to maintain treatment position for SBRT * Symptomatic emergent or other presentation precluding study development as planned (e.g., epidural compression of the spinal cord or cauda equina) * Previous chemotherapy, immunotherapy or target therapy