The aim of this randomized control trial was to determine the effects of 12-weeks of structured exercise training on the frequency of blood T-cell subsets associated with immunosenescence in a population of middle-aged/older women identified as being at high risk of developing breast cancer, and to correlate these with changes in serum levels of the muscle-derived cytokines (i.e. myokines) IL-6, IL-7, IL-15 and osteonectin. Here, IL15 is linked to breast carcinoma.