Targeting DNA repair in breast cancer.

Targeting of DNA repair is an important therapeutic approach in breast cancer, particularly for BRCA1/2 associated breast cancers and those characterized by a "BRCAness" phenotype including those with "triple negative" subtype. Various assays and scores have been developed to evaluate degree of homologous recombination deficiency in the hope that this would aid in predicting for susceptibility to DNA repair targeting agents, and yet, presence of a germline mutation in BRCA1/2 remains the strongest predictor for therapeutic efficacy of such agents. Pre-clinical studies suggested increased sensitivity to agents that damage DNA in a way that interferes with DNA replication forks and which subsequently require DNA repair by homologous recombination, such as platinum salts, and this data was further confirmed clinically. Recently published phase III data favor the use of PARP inhibitors amongst patients with BRCA1/2 associated advanced breast cancer. Novel chemotherapeutic agents targeting DNA damage repair are under evaluation as well as further combinations of PARP inhibitors with immuno-therapeutics and other biological agents.