[9] performed immunostaining of gamma-H2AX at 0.25, 3 and 6 h after 2 Gy of X-ray irradiation using PBLs from patients undergoing postoperative radiotherapy for breast cancer, and found a higher number of residual gamma-H2AX foci (i.e. lower DNA repair capacity) in patients with Grade 2 or 3 acute skin reaction to radiotherapy compared with the number of foci found in the no skin reaction group. Here, H2AX is linked to skin reaction.