A comprehensive meta-analysis of 17 studies spanning 8,314 records demonstrates that higher adherence to the Mediterranean diet reduces overall cancer mortality by 4%. The survival benefits varied dramatically by cancer type: gastric cancer patients experienced a remarkable 50% reduction in death risk, ovarian cancer patients saw 32% lower mortality, while breast and prostate cancers showed more modest 3% improvements. Disease-free survival improved most notably in breast cancer, with 61% better outcomes. This represents the most robust evidence to date for Mediterranean diet's role in tertiary cancer prevention—treatment after initial diagnosis. The finding carries profound implications for oncology care, suggesting dietary intervention could be as impactful as some pharmaceutical treatments. However, the research landscape remains limited by observational study designs that cannot prove causation, and the dramatic variation in effect sizes across cancer types suggests the Mediterranean diet's anti-inflammatory compounds may interact differently with various tumor microenvironments. While not paradigm-shifting, this evidence strengthens the case for integrating evidence-based nutritional counseling into standard cancer care protocols, offering patients an accessible, low-risk intervention that complements traditional treatments.