Association Between Red Blood Cell Distribution Width‐To‐Albumin Ratio and Breast, Colorectal, Lung, and Prostate Cancers

ABSTRACT Introduction Cancer remains a leading cause of global morbidity and mortality, underscoring the need for accessible biomarkers for early detection and risk stratification. The red blood cell distribution width‐to‐albumin ratio (RAR) integrates inflammation and nutritional markers often dysregulated in cancer. We evaluated RAR's association with a recent diagnosis (≤ 1 year) of breast, colorectal, lung, and prostate cancer in a representative US population. Methods Using National Health and Nutrition Examination Survey data (2005–2018), we conducted a cross‐sectional analysis of adults with recent diagnoses (≤ 1 year) of a single primary cancer. Propensity score matching balanced cases and cancer‐free comparisons by age, sex, and race. Weighted logistic regression assessed associations between a 1‐unit RAR (%dL/g) increase and cancer presence, reporting adjusted odds ratios (ORs) with 95% confidence intervals (CIs). Results The analysis included 48 breast, 31 colorectal, 19 lung, and 77 prostate cancer cases, along with their matched comparisons. A 1% dL/g increase in RAR was significantly associated with higher odds of breast (adjusted OR 1.62, 95% CI 1.17–2.24), colorectal (adjusted OR 1.56, 95% CI 1.01–2.40), and lung cancer (adjusted OR 1.95, 95% CI 1.44–2.66). No significant association was observed for prostate cancer (adjusted OR 1.05, 95% CI 0.69–1.59). Conclusion RAR is significantly associated with a recent diagnosis of breast, colorectal, and lung cancers, but not prostate cancer. These findings suggest RAR may reflect cancer‐associated systemic alterations, warranting further prospective study to validate its clinical applicability.