Do chemo- and radiotherapy affect the DNA repair ability of lymphocytes?

The DNA repair ability of unstimulated lymphocytes damaged by ultraviolet irradiation was measured in a group of 15 breast cancer patients before surgery, and 3 to 5 years later a) after surgery alone (n=6), or b) after surgery with additional chemo- and/or radiotherapy (n=9). In group a) 3 out of 6 patients had reduced repair before and 2 out of 6 after surgery. In the group b) 4 out of 9 patients had reduced repair before surgery, and 9 out of 9 after surgery plus chemo/radiotherapy. These results confirm our previous finding that chemo/radiotherapy influences DNA repair negatively. Because of the known association between reduced DNA repair and cancer occurrence, this could increase the risk of a secondary tumour.