Background Nowadays, different therapeutic options are available for the first-line treatment of metastatic renal cell carcinoma (mRCC). Immuno-combinations are the standard first-line therapy in all mRCC patients regardless of the International Metastatic RCC Database Consortium (IMDC) risk category, even though TKI monotherapy is still a therapeutic option in selected patients. However, comparisons between the different first-line treatment strategies are lacking and few real-world data are available in this setting. For this reason, the regimen choice represents an important issue in clinical practice and the optimal treatment sequence remains unclear. Methods The REGAL study is a multicentric prospective observational study enrolling mRCC patients treated with first-line systemic therapy according to clinical practice in a real-world setting. A retrospective cohort of mRCC patients who received first-line systemic therapy from the 1st of January 2021 will also be included. The primary objective is to identify potential prognostic and predictive factors that could help guide the treatment choice; secondary objectives included the assessment of the prognostic performance of the novel prognostic Meet-URO score (IMDC score + neutrophil-to-lymphocyte ratio + bone metastases) compared with the IMDC score and the comparison between treatment strategies according to response and survival outcomes and toxicity profile. Discussion Considering the high number of therapeutic first-line strategies available for mRCC, the identification of clinical prognostic and predictive factors to candidate patients to a preferable systemic therapy is still an unmet clinical need. The Meet-URO 33 study aims to provide a large-scale real-world database on mRCC patients, to identify the clinical predictive and prognostic factors and the different performances between the ICI-based combinations according to response, survival and toxicity. Trial Registration CESC IOV 2023-78. Keywords: Metastatic renal cell carcinoma, Immunotherapy, Immune checkpoint inhibitor, Clinical practice, Real-world, IMDC score, Meet-URO score, Prospective, Retrospective