Why your preferred targeted drugs may become unaffordable.

Trastuzumab, a monoclonal antibody directed at the HER2 receptor, is one of the most impressive targeted drugs developed in the last two decades. Indeed, when given in conjunction with chemotherapy, it improves the survival of women with HER2 positive breast cancer, both in advanced and in early disease. Its optimal duration, however, is poorly defined in both settings with a significant economic impact in the adjuvant setting where the drug is arbitrarily given for 1 year. This article reviews current attempts at shortening this treatment duration, emphasizing the likelihood of inconclusive results and, therefore, the need to investigate this important variable as part of the initial pivotal trials and with the support of public health systems. Failure to do so has major consequences on treatment affordability. Ongoing adjuvant trials of dual HER2 blockade, using trastuzumab in combination with a second anti-HER2 agent, and trials of the antibody-drug conjugate T-DM1 (trastuzumab-emtansine) have to all be designed with 12 months of targeted therapy.