How much atrial fibrillation is too much atrial fibrillation?

n engl j med 366;2 nejm.org january 12, 2012 178 tive anti-HER2 agents as adjuvant therapies may translate into metastatic disease developing in fewer patients. Given the success of the pivotal trials of adjuvant trastuzumab therapy, clinical trials of adjuvant therapies, which are already large and expensive, will by necessity require even more subjects to detect small differences with a new agent. These are challenges that ref lect the rewards of successful translational research, challenges we hope to face with other subsets of breast cancer.