Scott H. Kaufmann, MD, PhD

In this issue of ONCOLOGY, Comen and Robson provide a timely overview of poly(ADP-ribose) polymerase (PARP) inhibitors and their potential for the treatment of breast cancer. The authors highlight the recent demonstration of synthetic lethality between PARP inhibition and loss of either of the breast cancer susceptibility genes, BRCA1 and BRCA2, as well as the development of PARP inhibitors that are suitable for clinical therapy. However, many questions pertaining to both the basic biology of PARP inhibition and the potential clinical implications of PARP inhibitors still need to be addressed. In the following commentary, we highlight some of these remaining challenges.