MKI67 and breast cancer: The slight increase in Treg percentages that was observed at 4 and 8 weeks of treatment suggest the reduction in Tregs to be a temporary effect, as was previously also reported in advanced-stage breast cancer patients treated with single-agent 50 mg CTX p.o. daily [20] and which is in line with the observation of an increase in the expression of the proliferation marker Ki-67 in Tregs at time points 4 and 8 weeks.