The aim of the study is to evaluate the efficacy of radiotherapy on the primary site of gastroesophageal cancer and extracranial stereotactic radiotherapy on metastases before the use of standard systemic therapy, in cases of limited disease burden (in the experimental group), compared to the standard group, which does not receive radiotherapy. This prospective, multicenter, randomized trial aims to evaluate the efficacy of the unconventional approach versus the conventional one in increasing the percentage of asymptomatic patients due to the direct effect of the primary tumor or metastases. "Randomized" means that the assignment to one of the treatment groups mentioned above will be random, not influenced by the physician or the patient's condition. Therefore, your participation in either of the two treatments under study will be assigned randomly and not predetermined. This randomness is crucial for a proper analysis of the results at the end of the study, which will help clarify whether there are differences between the two proposed treatments. This also means that you may not receive direct benefits from participating in this study, as it is a research study.

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