Inter- and intra-tumoral heterogeneity in DNA damage evaluated by comet assay in early breast cancer patients

There are no clinical tools to functionally assess degree of DNA damage in breast cancer. The comet assay
is an accepted research tool for assessing DNA damage, however, most cancer studies have assessed
lymphocytes as surrogate cells. The aim of this pilot study was to use the comet assay in early breast
cancer directly in tumor tissue to compare DNA damage between and within traditionally defined
subgroups, and to explore intra-tumoral heterogeneity. Scrapings of tumor and healthy breast tissue
were obtained at primary surgery from 104 women. Comet assay was applied to quantitatively assess
DNA damage, revealing substantial inter- and intra-subgroup variation. Marked intra-tumoral heterogeneity
was evident across all subgroups. The degree of DNA damage for an individual could not be
predicted by breast cancer subgroup. Comet assay warrants further study as a potential clinical tool for
identification of tumoral DNA damage and ultimately, individualised use of DNA damaging therapy.