The comet assay in clinical practice

Thr comet assay is a single-cell gel electrophoresis technique that measure s DNA damage in individual cells. Since radiation produces 3-4 times more D NA damage in well-oxygenated cells compared with hypoxic cells. this assay can quantify the fraction of radiation-resistant hypoxic cells found in man y solid rumours. This paper summarizes our results with 73 accessible metas tatic tumours irradiated with palliative intent. Hypoxic fractions ranged f rom 0.0 to 0.67 with a mean of 0.15; 62% of these advanced rumours showed a hypoxic fraction > 0.05. Comparisons between two sequential aspirates in 3 3 tumours gave a slope of 0.92 (r(2) = 0.88), suggesting that a single aspi rate is generally representative of the tumour. A limitation, however, is t hat the hypoxic fraction could not be measured in clinical samples given a conventional dose of 2 Gy.