Previous research suggested that deficiencies in the ability of cells to repair damaged DNA added to the accumulation of DNA damage and sped up genetic changes associated with cancer development.

In this new study, researchers analyzed cell lines in blood samples taken from pairs of sisters. In each pair, one sister had developed breast cancer and the other was free of the disease.

The study found the sisters with breast cancer had much lower DNA repair capacity than the cancer-free sisters. Overall, deficient DNA repair capacity was associated with a two-fold increase in breast cancer risk. Women with the poorest DNA repair capacity had a breast cancer risk three times greater than women with the best DNA repair capacity.

"These data support the hypothesis that deficient DNA repair capacity is associated with susceptibility to breast cancer, and may be a valuable in vitro biomarker to identify high-risk subjects, especially in familial breast cancer families," the study authors wrote.

"It is unclear at this time whether there are any interventions that could alter DNA repair capacity and what effect such interventions might have on risk," the authors wrote.