Albumin–globulin ratio is a predictive biomarker of antitumour effect of immune checkpoint inhibitors in cancer patients

Immune checkpoint inhibitors (ICIs) have transformed cancer therapy, yet the heterogeneity of treatment responses underscores the need for reliable prognostic biomarkers. The albumin-to-globulin ratio (AGR), an indicator of systemic inflammation and nutritional status, has emerged as a potential predictor of ICI outcomes. This study aimed to systematically evaluate the prognostic significance of AGR in patients receiving ICIs through a meta-analysis and to validate the findings in a single-centre cohort. A systematic literature search was conducted using PubMed, EMBASE, and the Cochrane Library to identify studies published prior to June 6, 2025. The primary endpoints were overall survival (OS), progression-free survival (PFS), and disease control rate (DCR). In addition, a retrospective analysis was performed on a cohort of 74 patients with renal cell carcinoma (RCC) treated with ICIs at our institution to assess the prognostic value of baseline AGR in relation to OS and PFS. Seven studies encompassing 1,460 patients were included in the meta-analysis. Higher pretreatment AGR was significantly associated with improved OS (HR = 0.44; 95% CI: 0.30–0.66; <i>p</i> &lt; 0.001), extended PFS (HR = 0.61; 95% CI: 0.53–0.71; <i>p</i> &lt; 0.001), and superior DCR (OR = 4.48; 95% CI: 2.58–7.77; <i>p</i> &lt; 0.001). Sensitivity analyses confirmed the robustness of these associations. In our institutional RCC cohort, elevated AGR was independently linked to prolonged OS (<i>p</i> = 0.017) and PFS (<i>p</i> = 0.030), consistent with findings from the pooled data. AGR is a simple, inexpensive, and non-invasive biomarker with significant prognostic value in patients undergoing ICI therapy. These findings support its potential role in guiding clinical decision-making and optimizing patient selection for immunotherapy.