In an attempt to determine to which side the peripheral blood CD4+ Treg-Teff equilibrium tilts during anti-cancer therapies, we investigated the effects of metronomic (oral) vs. standard (intravenous) chemotherapy administration on the cell ratio of peripheral CD4+CD25+ Tregs and CD4+CD25- Teffs, and on the suppressive capacity of peripheral Tregs over Teffs, in patients with solid tumours. Here, CD4 is linked to cancer.