First-line Gemcitabine/Cisplatin +/- Avelumab in Locally Advanced or Metastatic Bladder Carcinoma

This study will assess efficacy (based on response rate) and safety (based on grade ≥ 3 severe adverse effects) of the combination Gemcitabine Cisplatin (GC) + anti-PD-L1 (avelumab) in first-line treatment for locally advanced or metastatic urothelial bladder cancer patients, after 6 cycles of treatment (or at 18 weeks if less than 6 cycles have been given, or earlier if a second line treatment is needed, before this new anticancer treatment has been started).