• Age ≥ 18 years

• Eastern Cooperative Oncology Group (ECOG) performance status ≤ 2

• Urothelial bladder cancer histologically proven (both pure urothelial cancers and mixed histologic features are allowed)

• Metastatic patients to regional nodes (Tx,N1-N3,M0) and/or distant sites (Tx,Nx,M1a-M1b) documented with contrast-enhanced CT-scanner of the chest, abdomen and pelvis, either de novo or presenting first regional/distant relapse following cystectomy (with no local recurrence in the cystectomy bed)

• Completion of the initial phase (4-6 cycles) of 1st line metastatic treatment (systemic therapy by chemotherapy and/or immunotherapy by immune check-point inhibitor according to standard recommendations). Patients having started maintenance therapy are eligible.

• No disease progression after the initial phase of first-line metastatic systemic therapy according to RECIST v1.1

• No more than 3 residual distant metastatic lesions following the initial phase of first-line metastatic systemic therapy:

∙ Regional nodes (below aortic bifurcation) are not included in the count of distant metastatic lesions

‣ The number of distant residual lesions is determined on the basis of the imaging modality for tumor response assessment performed after systemic treatment according to local habits (CT-scan or 18FDG PET-CT if performed):

∙ In case of response assessment by CT-scanner only: residual lesions are all remaining visible lesions In case of response assessment by additional 18FDG PET-CT: residual lesions are only the lesions with residual hyperfixation

‣ Regarding distant lymph nodes metastases:

⁃ If evaluation is performed by CT-scanner only, residual lymph nodes are considered pathological according to one or several criteria among: Short axis ≥ 1cm/Central necrosis/Heterogeneous contrast enhancement

• Residual para-aortic nodes involvement accounts for one lesion, even if several para-aortic nodes are involved.

• Other nodes: each involved node accounts for one lesion.

• Residual distant metastases (if applicable) eligible for SBRT in terms of dose constraints to the organs at risk, with no prior radiotherapy interfering with SBRT

• 8 weeks or less between last cycle of the initial phase of systemic treatment and randomization

⁃ No contraindication to pelvic radiotherapy

⁃ Signed informed consent

⁃ Patient able to participate and willing to give informed consent prior performance of any study-related procedures and to comply with the study protocol

⁃ Patient affiliated to a Social Health Insurance in France