DNA damage in peripheral blood lymphocytes of ovarian cancer patients after radiotherapy.

OBJECTIVE: Radiotherapy is a common mode of treatment for many types of cancer, particularly cancers that are not detected until late stages, as is common with ovarian cancer. Although radiotherapy is effective in preferentially killing tumor cells, DNA damage induced by ionizing radiation can also have toxic effects on non-tumor cells. The aim of this study was to investigate the extent of toxicity on non-tumor cells following radiotherapy for ovarian cancer. MATERIALS AND METHODS: The authors used the comet assay to assess DNA damage in peripheral blood lymphocytes of 60 ovarian cancer patients undergoing radiotherapy. Venous blood samples were collected from patients before radiotherapy and after accumulated doses of 10, 20, 30, 40, and 50 Gy of radiotherapy. RESULTS: Comet frequencies, reflecting the proportion of damaged cells, were significantly higher after radiotherapy than before radiotherapy (f = 69.66, p < 0.05) and demonstrated a linear relationship with accumulated dose (y = 9.87 + 0.2987x, r = 0.9497, p < 0.05). Additionally, the comet tail length, reflecting the relationship between undamaged and damaged DNA, was significantly longer after radiotherapy (f = 175.13, p < 0.05). CONCLUSIONS: These results demonstrate that radiotherapy induces DNA damage in lymphocytes of ovarian cancer patients and suggest that radiotherapy doses should be limited during clinical treatment to reduce toxic side-effects.