Bladder cancer is the most common type of urothelial cancer. When the disease has spread to other parts of the body (metastatic disease), the prognosis is often poor, because there are only a few effective treatment options available.

At the moment, standard treatment mainly includes systemic therapies, such as chemotherapy and immunotherapy (immune checkpoint inhibitors). These treatments act on the whole body. However, the use of local treatments, such as stereotactic radiotherapy, has not been well studied in bladder cancer.

Stereotactic radiotherapy is a type of radiation treatment that delivers very high doses of radiation to the tumor in a small number of treatment sessions. This technique is already widely used to treat a limited number of metastases (called oligometastases) from other types of cancer.

The aim of this study is to understand whether stereotactic radiotherapy is also effective and safe for treating oligometastases coming from bladder cancer.

Inclusion Criteria:

• Age > 18 years
• WHO performance status ≤ 2
• Pathological proven urothelial carcinoma
• Stage IV disease at imaging
• Maximum of 3 extracranial metastases
• Indication to receive I or II line of standard systemic therapy
• Adequate liver function
• Adequate bone marrow function
• Written informed consent

Exclusion Criteria:

• Inability to provide informed consent
• Previous radiation therapy on the same target lesions
• Pregnant or breastfeeding patients
• Prior malignancy within the last five years (except adequately treated basal cell carcinoma of the skin or in situ carcinoma of the skin or in situ carcinoma of the cervix, surgically cured, or localized prostate cancer without evidence of biochemical progression)
• Mental conditions rendering the patient incapable to understand the nature, scope, and consequences of the study
• WHO PS >=3