CD4 and lung cancer: Multiple courses of RT, RT sites, and RT doses increased the risk of RT-associated lymphopenia.[20] High RT doses were found to be a significant risk factor for lymphopenia in lung cancer patients.[20] Wang et al[8] showed that the immune parameters (percentages of CD3+, CD4+ T cells, and NK cell) were dramatically decreased after RT in the PTV volumes >300 cm3 group, whereas the percentage of CD8+ T cells increased, when compared with before RT.