This collection will bring together original research articles, reviews, and opinion pieces focused on the impact of social determinants of health on cancer incidence, clinical outcomes, treatment toxicity, and inequities in access and quality of care. While highlighting research conducted in Spain, it will also include international contributions to situate national evidence within a broader comparative and global framework. The aim of the collection is to advance understanding of how factors such as socioeconomic status, education, occupation, ethnicity, geographic context, and healthcare accessibility shape cancer trajectories, while promoting a debate with implications for clinical practice, translational research, and health policy.