Le Cornet C, Schildknecht K, Chornet AR, et al. - Given the existence of sufficient evidence suggesting the importance of immune cell homeostasis as a prognostic outcome determinant in cancer patients, and considering that few studies have investigated if it also ascertains cancer risk in initially healthy people, researchers undertook a case-cohort analysis involving incident cases of breast (n = 207), colorectal (n = 111), lung (n = 70), and prostate (n = 201) cancer and a subcohort (n = 465) within the European Prospective Investigation into Cancer and Nutrition (EPIC)-Heidelberg cohort in order to estimate the links between relative counts of immune cell and cancer risks. A significant positive link between relative counts of FOXP3+ regulatory T-cells (Tregs) and lung cancer risk, and significant inverse links between relative CD8+ counts and risks of lung and breast cancer (overall and ER+ subtype) were identified when relative counts of immune cell types were considered individually. Further significant positive links between higher relative FOXP3+ T-cell counts and elevated risks of colorectal and breast cancer (overall and ER- subtype) were revealed in multivariable models with mutual adjustments across immune markers. Findings revealed no links between immune cell composition and prostate cancer risk. Based on these findings, it was inferred that elevated FOXP3+ Tregs and lower levels of cytotoxic (CD8+) T-cells hold relevance as risk factors for tumor development.