All samples were from primary breast cancers treated with pre-surgical ("neoadjuvant") therapy in controlled studies from which TP53 and CHEK2 gene mutation status had been previously characterized and the direct response to chemotherapy (doxorubicin, 5FU/mitomycin or epirubicin) as well as long-term outcome for each individual patient determined. Here, CHEK2 is linked to breast cancer.